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Article

Valorization of Spent Coffee Grounds as a Substrate for Fungal Laccase Production and Biosorbents for Textile Dye Decolorization

by
Eduardo da Silva França
1,
Adriana Ferreira de Souza
2,
Dayana Montero Rodríguez
2,
Nazareth Zimiani de Paula
3,
Anna Gabrielly Duarte Neves
4,
Kethylen Barbara Barbosa Cardoso
5,
Galba Maria de Campos-Takaki
2,
Marcos Antonio Barbosa de Lima
3,* and
Ana Lucia Figueiredo Porto
4
1
Postgraduate Program in Biotechnology–Northeast Biotechnology Network, Federal Rural University of Pernambuco, Recife 52171-900, PE, Brazil
2
Multiuser Center for Analysis and Characterization of Biomolecules and Surface Materials, Catholic University of Pernambuco, Recife 50050-900, PE, Brazil
3
Agricultural and Environmental Microbiology Laboratory, Department of Biology, Federal Rural University of Pernambuco, Recife 52171-900, PE, Brazil
4
Laboratory of Advances in Protein Biotechnology and Bioactive Technology, Department of Animal Morphology and Physiology, Federal Rural University of Pernambuco, Recife 52171-900, PE, Brazil
5
Biology Applied to Health Program, Federal University of Pernambuco, Recife 50670-901, PE, Brazil
*
Author to whom correspondence should be addressed.
Fermentation 2025, 11(7), 396; https://doi.org/10.3390/fermentation11070396
Submission received: 1 June 2025 / Revised: 5 July 2025 / Accepted: 5 July 2025 / Published: 10 July 2025
(This article belongs to the Special Issue Application and Research of Solid State Fermentation, 2nd Edition)
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Abstract

Spent coffee grounds (SCG) are a widely available agro-industrial residue rich in carbon and phenolic compounds, presenting significant potential for biotechnological valorization. This study evaluated the use of SCG as a suitable substrate for fungal laccase production and the application of the resulting fermented biomass (RFB), a mixture of fermented SCG and fungal biomass as a biosorbent for textile dye removal. Two fungal strains, namely Lentinus crinitus UCP 1206 and Trametes sp. UCP 1244, were evaluated in both submerged (SmF) and solid-state fermentation (SSF) using SCG. L. crinitus showed superior performance in SSF, reaching 14.62 U/g of laccase activity. Factorial design revealed that a lower SCG amount (5 g) and higher moisture (80%) and temperature (30 °C ± 0.2) favored enzyme production. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses confirmed significant structural degradation of SCG after fermentation, especially in SSF. Furthermore, SCG and RFB were chemically activated and evaluated as biosorbents. The activated carbon from SCG (ACSCG) and RFB (ACRFB) exhibited high removal efficiencies for Remazol dyes, comparable to commercial activated carbon. These findings highlight the potential of SCG as a low-cost, sustainable resource for enzyme production and wastewater treatment, contributing to circular bioeconomy strategies.

1. Introduction

The growing demand for food and agro-industrial products due to the rapid growth of the global population results in linear agricultural production that generates large amounts of waste [1]. However, these residues represent a significant loss of biomass and nutrients that can be reused in various industries, such as the pharmaceutical, food, chemical, and industrial biotechnology industries, to formulate culture media for the microbial production of various biomolecules in a sustainable way [2].
A relevant example of this waste is spent coffee grounds (SCG), a widely available byproduct. It is estimated that approximately 90% of the coffee consumed worldwide is discarded as solid waste. Brazil is the largest producer and exporter of coffee, generating a large volume of solid waste [3]. In the production of soluble coffee, it is estimated that for each ton of green coffee processed, 650 kg of SCG are generated, and for each kg of soluble coffee produced, 2 kg of SCG are generated, which contain significant concentrations of tannin and caffeine and can cause environmental damage if disposed of incorrectly [4].
SCG represents a promising source for reuse in sustainable bioprocesses due to its high carbon content, phenolic compounds, and residual nutrients [5]. One of the high added-value alternative destinations for this waste is its use as a substrate for fungal fermentation aimed at the production of enzymes of industrial interest [6]. In this context, white-rot basidiomycetes can produce a nonspecific enzyme complex capable of degrading plant cell wall components, such as lignin, which is considered highly recalcitrant. This enzyme complex is composed of enzymes, such as laccase, manganese peroxidase, lignin peroxidase, and versatile peroxidases [7,8].
Laccases (EC 1.10.3.2) exhibit a high substrate specificity and are applied in various industrial and environmental technologies, including the treatment of textile effluents [9]. For their effective implementation in different industries, a cost-effective method for continuous laccase production is essential. Fungi can produce laccase through two main methods, namely solid-state fermentation (SSF) and submerged fermentation (SmF). Of these, SSF is often preferred because it mimics the natural growth conditions of fungi, characterized by low moisture content, which promotes optimal fungal development and leads to more efficient enzyme production [10].
Furthermore, fermented SCG can still be reused as a biosorbent for removing textile dyes, particularly those from the Remazol class, thereby further enhancing their added value. This approach aligns with the principles of a circular biorefinery, in which waste materials are valorized through multiple successive stages [11]. The application of biosorbents for dye removal is particularly relevant, given the severe environmental impact of synthetic dyes, which are widely used in the textile industry. These compounds pose a significant threat to aquatic fauna and flora due to their ability to disrupt hormonal, genetic, and endocrine functions. Moreover, many are known to be mutagenic and carcinogenic, posing serious risks to human health, including chronic kidney diseases and central nervous system disorders [12].
Considering this scenario, this study aimed to investigate the feasibility of SCG as a substrate for producing fungal laccase and subsequently to evaluate the potential of the resulting fermented biomass (RFB) as a biosorbent for removing synthetic textile dyes.

2. Materials and Methods

2.1. Microorganisms

The fungi Lentinus crinitus UCP 1206 and Trametes sp. UCP 1244 were kindly provided by the Culture Collection of the Catholic University of Pernambuco UCP (Recife, PE, Brazil), located at the Multiuser Center for Analysis and Characterization of Biomolecules and Material Surfaces (CEMACBIOS). The strains were maintained in potato dextrose agar (PDA), pH 5.6 ± 0.2, under refrigeration at 5 ± 0.2 °C and in continuous replication every 6 months.

2.2. Spent Coffee Grounds (SCG)

The SCG was kindly provided by coffee shops and residences located in Recife, PE and then taken to a forced-air oven (Marconi brand, model MA035) at 65 ± 0.2 °C until it reached 10% moisture, after which it was cooled to 28 ± 0.2 °C for 2 h. The moisture was determined using a moisture analyzer (Shimadzu brand, model MOC-63U). After drying, the samples were homogenized and stored in hermetic polypropylene containers, remaining at a controlled room temperature of 28 ± 0.2 °C until use. The granulometric analysis of the SCG was carried out using a series of standardized sieves according to ASTM/Tyler standards, with openings corresponding to mesh sizes of 18, 32, 48, 60, 100, 150, 200, and 325.

2.3. Laccase Production

The inoculum was prepared according to the methodology described by Himanshu et al. [13]. Briefly, the fungi L. crinitus UCP 1206 and Trametes sp. UCP 1244 were cultivated in PDA culture medium, pH 5.6 ± 0.2, and incubated in an incubator (Brand Solidsteel, model SKU: SSBOD120L-110) at 28 °C ± 0.2 for 5 days. Subsequently, four mycelium discs of 5 mm in diameter were used as inoculum for SmF and SSF tests to produce laccase using SCG as a substrate. SmF was performed in triplicate using 250 mL Erlenmeyer flasks containing 100 mL of salt solution medium (KH2PO4 1.5 g/L, MgSO4 0.5 g/L, KCl 0.5 g/L, FeSO4 0.036 g/L, and ZnSO4 0.035 g/L) [7], and 10 g of SCG with particle sizes between 0.045 mm (2.8%), 0.15 mm (5%), 0.25 mm (5%), 0.3 mm (46.1%), 0.5 mm (38.2%), and 1.0 mm (2.9%). They were then incubated at 28 ± 0.2 °C under orbital shaking at 150 rpm for 15 days. In turn, SSF was carried out in triplicate using 250 mL Erlenmeyer flasks containing 10 g of SCG with the moisture content adjusted to 60% by the addition of the salt solution, as described by Cardoso et al. [7], pH 5.6 ± 0.2, and incubated at 28 °C ± 0.2 for 15 days. After the SSF process, the enzymatic extract was removed by adding 50 mL of 10 mM sodium acetate buffer, pH 5.0 ± 0.2, and then subjected to orbital agitation at 150 rpm at 28 °C ± 0.2 for 1 h. In both assays, the crude enzymatic extract was obtained by filtration through a nylon membrane (mesh 60), followed by centrifugation at 6000 rpm at 4 °C ± 0.2 for 10 min to remove the residual biomass [13].

2.4. Determination of Laccase Activity

Laccase activity was determined according to Ranimol et al. [14], with modifications. The reaction was carried out in a 3 mL mixture containing 1 mL of 2 mM guaiacol, 1 mL of 10 mM sodium acetate buffer (pH 5.0 ± 0.2), and 1 mL of enzyme extract. The mixture was incubated for 20 min at 28 ± 0.2 °C. Absorbance was then measured at 450 nm using a UV–visible spectrophotometer (Libra S32 model, Biochrom Ltd., Cambridge, UK). Laccase activity was defined as the amount of enzyme required to oxidize 1 µmol of guaiacol per minute and was calculated as EA = (A × V)/(t × ɛ × v), where EA = enzyme activity; A = absorbance; V = total reaction volume (mL); v = volume of enzyme extract (mL); t = incubation time (min); ɛ = extinction coefficient of guaiacol (0.6740 mM/cm−1). The results were expressed in international units (U) per gram of substrate on a dry weight basis. The laccase activity reported here corresponds to crude extracts. No specific purification or structural analysis of the laccase isoforms was performed.

2.5. Full-Factorial Design

A 23 full-factorial design (FFD) with 4 replicates at the central point was conducted to evaluate the influence of the independent variables (SCG amount, moisture, and temperature) on laccase activity as the response variable. Each independent variable was investigated at three levels, namely minimum (−1), central (0), and maximum (+1), as shown in Table 1. The data were analyzed using STATISTICA software, version 12, with a significance level of p < 0.05. The tests were conducted in SSF using the fungus selected in the preliminary tests for laccase production.

2.6. Identification of Structural Changes in SCG

The SCG were subjected to FTIR spectroscopic analysis and scanning electron microscopy (SEM) before and after the SmF and SSF processes to identify the occurrence of structural changes. FTIR spectroscopy was performed using Shimadzu IRSpirit equipment, in the range of 4000 to 500 cm−1 at 4 cm−1 of resolution and with 45 scans for each display. For the SEM, the samples were collected, washed with phosphate-buffered saline (PBS) at pH 7.0, then frozen in an ultrafreezer (ColdLab, Piracicaba, SP, Brazil) at −40 °C ± 0.2 for 24 h and lyophilized in an Advantage Plus EL-85 lyophilizer (SP Scientific, Stoneridge, NY, USA). Subsequently, the samples were mounted on aluminum stubs and coated with a gold layer approximately 10 nm thick using a Smart Coater DII-29010SCTR (JEOL Ltd., Tokyo, Japan). They were then examined using a scanning electron microscope (SEM), model JSM-5600LV (JEOL Ltd., Tokyo, Japan), operating at an accelerating voltage of 10 kV.

2.7. Determination of Protein Concentration and Phenolic Compound Content in SCG

The determination of total protein and phenolic compounds in SCG was performed before and after SSF. The SCG extracts were obtained by adding 10 g of the SCG to 100 mL of distilled water, and then they were heated at 95 °C ± 0.2 for 4 min under agitation, filtered through a nylon membrane (mesh 60), and centrifuged at 6000 rpm at 28 °C ± 0.2 for 10 min [15]. The total protein content was measured using a commercial bicinchoninic acid (BCA) assay kit (Thermo Scientific, Waltham, MA, USA), according to the manufacturer’s instructions. Samples were analyzed in triplicate. Quantification was based on a bovine serum albumin (BSA) calibration curve, with the equation y = 0.5241x + 0.0653 (R2 = 0.9979), and the results were expressed in mg/mL.
The total phenolic compounds (TPC) concentration was determined as described by Seo and Park [16], with modifications, using 3.25 mL of reaction mixture composed of 2.75 mL of 3% Folin–Ciocalteu reagent and 0.25 mL of extract. The mixture was vortexed for 10 s and incubated at room temperature (28 °C ± 0.2) for 5 min. Then, 0.25 mL of 10% sodium carbonate solution was added. The mixture was vortexed again for 10 s and incubated in the dark at room temperature (28 °C ± 0.2) for 1 h. After incubation, absorbance was measured at 765 nm. A reaction blank was prepared using 0.25 mL of distilled water and 2.75 mL of 3% Folin–Ciocalteu reagent. Quantification was based on a calibration curve constructed using gallic acid as the standard. The calibration equation was y = 0.0473x + 0.0726 (R2 = 0.9993). The results were expressed as milligrams of gallic acid equivalent per gram of dry SCG (mg GAE/g).

2.8. Effect of pH and Temperature on Laccase Activity and Stability

The effect of pH and temperature on the activity of laccase, as well as the stability in crude extract, was evaluated using the method described by Gutiérrez-Antón et al. [17]. The effect of pH was determined by pre-incubation of the crude extract at 28 °C ± 0.2 for 10 min, at pH values ranging from 2.0 to 10.0 in 100 mM of citrate buffer (pH 2.0–3.0 ± 0.2 ± 0.2), acetate buffer (pH 4.0–5.0 ± 0.2), phosphate buffer (pH 6.0–7.0 ± 0.2) and sodium carbonate buffer (pH 8.0–9.0 ± 0.2). The effect of temperature on laccase activity was evaluated by pre-incubating the crude extract in a temperature range of 20–80 °C ± 0.2 for 10 min at the optimal pH. The initial enzyme activity without any treatment was considered as 100%, and the relative activity was calculated as a percentage. The pH stability was determined by pre-incubation of the crude extract in the buffers (with pH ranging from 2.0 to 10.0) at 28 °C ± 0.2 for 1, 3, 5, and 24 h. The thermostability of laccase was determined by incubating the crude enzyme extract at temperatures ranging from 20 °C to 80 °C ± 0.2 for 1, 3, 5, and 24 h. The reaction samples were pre-incubated at 28 °C ± 0.2 for 20 min at the optimal pH. Relative activity was considered as 100%, and residual activity was calculated as a percentage. REA% = (REA/RA) × 100, where REA = residual activity (%); REA = residual enzyme activity; RA = relative enzyme activity.

2.9. Preparation of Biosorbents

Different procedures were carried out to prepare the biosorbents, as described below.
  • Activated carbons: Activated carbon from SCG (ACSCG) and activated carbon from RFB (RFBAC) were prepared following the methodology of Prabawati et al. [18] with modifications. Initially, both SCG and RFB were separately impregnated with phosphoric acid (H3PO4) at a concentration of 85% in a 1:1 (w/v) ratio. The impregnated samples were dried in a forced-air circulating oven (Marconi, model MA035, Brazil) at 105 °C ± 0.2 for 24 h. After drying, the materials were carbonized in a muffle furnace at 400 °C ± 0.2 for 2 h.
  • Acid treatment: The same methodology of impregnation with H3PO4 and subsequent drying was used, as described above. The residual acid was removed by repeated washes with distilled water, followed by drying at 65 °C ± 0.2 until complete dehydration. Acid-treated SCG (ATSCG) and acid-treated RFB (ATRFB) were then obtained.
  • Biochars: The biochars of SCG (BSCG) and RFB (BRFB) were prepared by carbonizing the samples at 400 °C ± 0.2 for 2 h.
  • Lyophilization: Lyophilized RFB (LRFB) was obtained after freezing at −40 °C for 24 h and lyophilization for 72 h in an Advantage Plus EL-85 lyophilizer (SP Scientific, Warminster, PA, USA). The lyophilized material was stored in desiccators and later kept in hermetically sealed containers until further use.

2.10. Adsorption Assay

For the adsorption assays of Remazol dyes, the previously described biosorbents were used, along with unfermented SCG and commercial activated carbon (CAC) powder (ISOFAR, Brazil) for comparison. The experiments were conducted according to the methodology described by Tigrine et al. [19] with modifications. Briefly, 1.0 g of each adsorbent was added to 125 mL Erlenmeyer flasks containing 50 mL of a 100 mg/L solution of the Remazol textile dye (yellow, black, or red). The flasks were incubated at 28 °C ± 0.2 with orbital shaking at 150 rpm for 24 h, in triplicate. Then, the samples were filtered through a nylon membrane (mesh 60) to separate the adsorbent. The filtrate was centrifuged at 6000 rpm at 28 °C ± 0.2 for 10 min to remove the residual adsorbent from the filtration. The supernatant was used to quantify the concentration of the dyes by spectrophotometry based on the absorbance values of the Remazol Yellow (417 nm), Remazol Black (600 nm), and Remazol Red (518 nm) dyes. The measurements were performed in triplicate in a UV–visible spectrophotometer (model Libra S32, Biochrom Ltd., Cambridge, UK). The quantification was based on a calibration curve of the dyes (10–100 mg/L), using the following equations: Remazol Yellow (y = 0.0245x − 0.0241 and R2 = 0.9959), Remazol Black (y = 0.278x + 0.0153 and R2 = 0.9997), Remazol Red (y = 0.0196x + 0.028 and R2 = 0.9985). Before and after the adsorption test, the adsorbents were analyzed by FTIR in the range of 4000 to 500 cm−1 to identify the functional groups.

3. Results and Discussion

3.1. Production of Fungal Laccase Using SCG

SmF and SSF tests were conducted using L. crinitus UCP 1206 and Trametes sp. UCP 1244 to evaluate their potential for laccase production using SCG as substrate, and to compare the effectiveness of the two fermentation strategies. The results demonstrated that L. crinitus UCP 1206 exhibited a superior ability to produce laccase under both fermentation conditions. In SSF, this strain achieved a significantly higher enzymatic activity of 14.62 U/g, compared to 4.7 U/g observed in SmF. These findings highlight the efficiency of L. crinitus under solid-state conditions, indicating that SSF is more favorable for laccase production when using SCG as a sustainable substrate. On the other hand, Trametes sp. UCP 1244 showed no laccase activity under SSF and demonstrated a low activity of 3.7 U/g in SmF. These results indicate a limited capacity of Trametes sp. UCP 1244 to produce laccase using SCG as a substrate, particularly when compared to the superior performance of L. crinitus UCP 1206. Future research should investigate the structural and functional diversity of the laccases produced by these fungi.
Furthermore, the comparison between SSF and SmF highlights the influence of fermentation type on enzyme production efficiency, with SSF proving to be more advantageous for L. crinitus UCP 1206 cultivated on SCG. SSF more faithfully reproduces the natural environment of the microorganism, in addition to providing greater recovery of the product [20]. Hasan et al. [21] reported that SSF produces enzymes with greater stability in terms of temperature and pH compared to SmF. They also observed that low or absent enzyme production in SmF may be due to the microorganisms requiring a longer adaptation period before achieving significant enzyme production.
In addition, SSF can use agro-industrial waste as a feasible alternative substrates, which simultaneously serves as a support and source of nutrients for microbial growth, with filamentous fungi being the best adapted to these conditions. In this context, several researchers have described the use of a wide range of organic residues as cheap substrates for the production of lignocellulosic enzymes in SSF, including brewer’s spent grain, rice bran, wheat bran, grape pomace, coffee husk, wood chips, and olive pomace [22,23,24,25]. Table 2 shows recent studies reporting laccase production by white-rot fungi using agro-industrial waste, in comparison with our results using SCG. The choice of an appropriate substrate influences the successful production of enzymes. In this sense, SCG prove to be a suitable substrate for achieving high enzyme levels, resulting in a considerable reduction in laccase production costs and contributing to environmental protection through waste recycling.

3.2. Production of Laccase by L. crinitus in SSF

Laccase production via SSF is strongly influenced by various operational parameters, including substrate amount, moisture content, and temperature, as well as the interactions among these factors. In this context, a 23 FFD was applied in the present study to investigate the individual and combined effects of these factors on the activity of laccase produced by L. crinitus UCP 1206 under solid-state conditions. According to the results shown in Table 3, laccase activity varied from 0.16 to 23.78 U/g, with the highest result at 5 g of substrate, 80% moisture, and 30 °C of temperature (condition 7).
The low production of laccase in larger quantities of substrate is related to the time required for the fungus to establish itself and begin degrading the substrate, which can vary according to environmental conditions, such as moisture and temperature. The results obtained regarding moisture and temperature corroborate with Bellettini et al. [32], which indicated that the optimal temperature for the growth of basidiomycetes is 25–30 °C, and the appropriate moisture should cover a range of 60–80%.
The analysis of variance (ANOVA) conducted for the 23 FFD revealed that the 3 studied factors had statistically significant effects on laccase activity (p < 0.05). SCG amount and moisture were the most influential, followed by temperature. Also, a significant interaction was observed between SCG amount and moisture, suggesting that the effect of one depends on the level of the other. Other factor interactions were not significant (p > 0.05). The model demonstrated a good fit to the experimental data, with a coefficient of determination (R2) of 0.918, indicating that the independent variables and their interactions explained 91.8% of the variability in enzymatic activity. The mean square pure error (1.305) represents the natural variability observed among the replicates at the central point, which served as a baseline for assessing the statistical significance of the effects in the FFD.
The Pareto chart shown in Figure 1 confirmed the significant effects of the studied factors on laccase activity. The SCG amount exhibited a negative effect on laccase activity, indicating that high values may inhibit enzyme production, probably due to the physical limitation caused by the compaction of SCG, or also due to the incubation time. On the other hand, moisture displayed a positive effect, suggesting that wetter conditions favor the diffusion of nutrients and the enzyme’s performance. Temperature also showed a positive influence on laccase activity, indicating that the enzyme activity increased with increasing temperature.
Additionally, the interaction between SCG amount and moisture revealed a significant and negative effect, indicating that increasing both factors simultaneously leads to a reduction in the expected enzyme activity. This finding demonstrates an antagonistic relationship where, for example, very high moisture levels may inhibit the effective use of SCG as a substrate, possibly due to reduced oxygen availability. Figure 2 displays the response surface generated for these two variables (SCG amount and moisture), with a constant temperature of 28 °C, indicating that the highest levels of laccase activity were observed under conditions of low substrate amount and high moisture. It confirms the trend identified in the Pareto chart and suggests that maintaining a moderate substrate amount is essential to avoid inhibitory effects, whereas adjusting the moisture is a critical factor for optimizing the process.
These results support the importance of optimizing the variables involved in the laccase production using agro-industrial waste, such as SCG. Although future studies should address the adaptation of the process and equipment on a larger scale, the use of abundant and low-cost inputs suggests a promising economic viability for application at the pilot or industrial scales, contributing to a more efficient and sustainable biotechnological system.

3.3. Identification of Structural Changes in SCG After Fermentation

The FTIR spectra of SCG before and after SmF and SSF showed structural and functional modifications resulting from the fermentation processes (Figure 3). A slight intensity reduction of the band around 3309 cm−1 was observed, particularly after SSF, associated with the vibrational stretching of hydroxyl groups (O–H), typical of alcohols, phenols, carboxylic acids, and residual water [33]. The bands at 2922 and 2853 cm−1, attributed to the stretching of C–H bonds, also showed a reduction, suggesting the possible degradation of lipids and lateral structures of lignin. According to Okur et al. [34], these peaks correspond to the asymmetric and symmetric vibration of C-H in lipids, composed of long chains of linear aliphatic substances, which can be partially attributed to the unsaturated and saturated lipids present in coffee oils, known for not changing after roasting.
The absorption bands at 2422 and 2161 cm−1, attributed to C≡C triple bond stretching vibrations, exhibited a significant attenuation in the spectrum of SCG after SSF, suggesting the modification or consumption of alkyne-containing compounds or unsaturated chain structures. Moreover, the peak observed at 2161 cm−1 is characteristic of C≡C bonds, often associated with overtone and combination bands arising from aromatic compounds. This signal is attributed to the combination bands of phenolic compounds, such as ferulic and coumaric acids and their derivatives [35].
The most evident changes occurred in the region from 2000 to 1500 cm−1, in the bands at 1710, 1631, 1371, 1246, 1156, and 1028 cm−1, related to carbonyl groups C=O, double bonds C=C, and C-O bonds, as well as phenolic structures typical of carbonyls found in alcohols, carboxylic acids, esters, or oxidized phenolic compounds. The reduced intensity of these bands in the spectrum of SCG after SSF indicates a more significant degradation of phenolic compounds, cellulose, hemicellulose, and lignin, resulting from the enzymatic activity of the fungus. The peak detected at 1710 cm−1 is attributed to CO and the asymmetric stretching present in lignin [36]. The intense peak at 1028 cm−1 is specific to C–O bonds in the cellulose and hemicellulose band and to the C-OH bending vibration of xylenes [37]. In the lower region of 1000 cm−1, the bands at 867, 675, and 525 cm−1 stand out, and they are associated with out-of-plane bending vibrations of C–H bonds in aromatic rings, typical of complex phenolic compounds, as well as C–C and C–O bonds in cyclic structures or aromatic polymers derived from lignin.
Also, the micrographs presented in Figure 4 show the surface morphology of SCG before and after the SmF and SSF processes. In Figure 4A,B, the unfermented SCG particles exhibit a compact and relatively uniform surface, with a dense and continuous texture and low apparent porosity. These features reflect the undegraded lignocellulosic structures, indicating a structural matrix rich in cellulose, hemicellulose, and intact lignin, as reported by Mariana et al. [38] and Roychand et al. [39].
In Figure 4C,D, the SCG particles after SmF show a slight disorganization of the surface matrix, with increased porosity and the presence of cracks and partial erosions. The enzymatic action of the fungus L. crinitus in a liquid medium appears to have promoted moderate structural modifications, indicating the initial degradation of components, such as hemicellulose and phenolic compounds, while still preserving the original structure to some extent.
In Figure 4E,F, the SCG particles after SSF show a highly fragmented, porous, and fibrillated surface, indicating intense degradation of the lignocellulosic matrix. The collapsed structure and the evidence of fibrous networks are indicative of efficient enzymatic action on cellulose and lignin, which promoted significant structural changes in the surface of the SCG particles. The observed increase in porosity and degradation of the matrix indicates greater efficiency of the fungus L. crinitus in the bioconversion of lignocellulosic constituents of SCG by SSF. These features are consistent with the spectroscopic data from FTIR (Figure 3), which also indicates greater chemical modification under these conditions.

3.4. Total Protein and Phenolic Compound Content of SCG

The total protein content in the SCG was 4.74 ± 0.12 mg/mL, significantly increasing to 9.48 ± 0.09 mg/mL after the SSF process. This increase reflects the production of extracellular enzymes during the degradation of biomass by the fungus L. crinitus UCP 1206. According to Ganash et al. [40], the quantification of total proteins does not provide specific information about the activity of individual enzymes. Fungal strains with high protein secretion may exhibit low laccase activity, despite actively producing other lignocellulolytic enzymes, such as cellulases, hemicellulases, and peroxidases.
Regarding the total phenolic compounds, a considerable reduction was observed, decreasing from 66.55 ± 0.01 mg GAE/g before fermentation to 24.69 ± 0.01 mg GAE/g after SSF. This decrease indicates the degradation of phenolic compounds because of enzymatic action on the lignocellulosic structure of SCG. Phenolic compounds, such as ferulic acid, p-coumaric acid, and their derivatives, are components of lignin and the cell wall and are susceptible to oxidation by enzymes such as laccases. Previous studies indicate significant variations in the levels of phenolic compounds in SCG, depending on the origin and extraction method. Andrade et al. [41] reported values of 53.7 ± 3.1 mg GAE/100 g for Brazilian SCG and 41.6 ± 2.1 mg GAE/100 g for Colombian SCG, highlighting that edaphoclimatic factors (such as the temperature, moisture, altitude, and geographical location) influence the biosynthesis of these secondary metabolites in coffee plants. Furthermore, the extraction method is crucial for the efficiency in recovering phenolics. For instance, Abbasi-Parizad et al. [42] obtained 22.77 mg GAE/g using 70% ethanol extraction, while Ozuna et al. [43] reported 23.37 mg GAE/g using water at 95 °C. Thus, the results demonstrate that SSF with L. crinitus not only promotes the production of proteins related to extracellular enzymes but also significantly reduces the content of phenolic compounds, confirming the degradative activity on the lignocellulosic matrix of the SCG.

3.5. Effect of pH and Temperature on Laccase Activity and Stability

The effect of pH on the activity of laccase produced by L. crinitus UCP 1206 on SSF is presented in Figure 5A. A progressive increase in enzymatic activity was observed between pH 2.0 and 4.0, reaching the relative enzymatic activity (93.04%) at pH 4.0. Starting from pH 5.0, the activity underwent a sharp decline, indicating the enzyme’s sensitivity to less acidic environments. This behavior is consistent with the acidic profile commonly reported for fungal laccases. Previous studies show similar optimal pH values for laccases produced by Lentinula edodes [44] and Aspergillus sp. [45]. According to Hasan et al. [21], the optimal pH range for maximum activity of fungal laccases varies between 4.0 and 6.0, depending on the producing species. For example, Agrocybe pediades showed optimal activity at pH 5.0 [46], while Coriolopsis gallica exhibited the highest activity at pH 6.0 [47].
Furthermore, the effect of temperature on laccase activity was investigated in the range of 20 to 80 °C. According to Figure 5B, laccase activity increased between 20 and 50 °C and decreased starting from 60 °C, with the highest enzymatic activity between 40–50 °C (100% relative enzymatic activity). These results are similar to the optimal temperature values reported for laccases from Ganoderma leucocontextum [48].
Regarding the stability against pH (Figure 5C), laccase maintained more than 60% of its original activity after 24 h of incubation at 28 °C within the pH range of 3.0 to 6.0, indicating good stability under slightly acidic conditions. Concerning thermal stability (Figure 5D), the enzyme remained stable for up to 1 h between 20 and 40 °C, with a gradual reduction in activity over 24 h of incubation. Notably, laccase maintained 79.94% of its activity after 5 h at 60 °C, demonstrating significant thermal tolerance up to that point. Starting from 70 °C, the activity drastically decreased, with a complete loss of enzymatic activity observed at 80 °C. A similar behavior was described for the laccase from Ganoderma australe by Si et al. [49]. These researchers suggested that the decline in enzyme activity at certain pH levels may result from surface charge alterations that affect enzyme and substrate structures, thereby influencing the reaction catalysis. They also stated that high temperatures reduce enzyme activity due to thermal deactivation and irreversible protein unfolding.
These results reinforce the biotechnological potential of laccase produced by L. crinitus UCP 1206, particularly in applications that require acidic conditions and moderately elevated temperatures, without increasing operational costs and energy demands.

3.6. Characterization of the Biosorbents

In Figure 6, the FTIR spectra of the biosorbents are presented, enabling the identification of functional groups and the structural changes resulting from the applied treatments.
In Figure 6A, the spectrum of the CAC exhibits lower transmittance values throughout the entire spectral range, which is characteristic of materials with high chemical complexity and a high degree of carbon condensation. This behavior is attributed to the harsh production conditions of CAC, typically involving temperatures above 600 °C, under which most surface functional groups are degraded, as reported by Campbell et al. [50]. This degradation explains the absence of well-defined peaks in the FTIR spectrum.
Concerning the biosorbents based on SCG, a significant reduction is observed in the bands located in the region between 4000 and 2000 cm−1, when comparing the spectra of SCG, ACSCG, and BSCG (Figure 6A). This decrease may be associated with the decomposition of volatile functional groups, such as hydroxyls and aliphatic chains, during the pyrolysis process [51]. The loss of these bands indicates a structural transformation in the materials, resulting in more stable and less functionalized surfaces, especially in the carbonized adsorbents. Furthermore, the ACSCG exhibits more intense bands than the SCG in the region between 2000 and 1000 cm−1, at around 1561 cm−1, which is attributed to the stretching vibrations of C=C bonds in aromatic rings formed during pyrolysis. Additionally, a broad band observed between 1600 and 1000 cm−1 may be attributed to P=O and P-O-C vibrations associated with H3PO4 activation combined with pyrolysis. Similar changes in activated carbons from SCG were reported by Aouay et al. [52].
For the ATSCG, the spectrum exhibits a slight reduction in functional groups compared to the SCG, which can be attributed to the degradation of compounds resulting from the interaction of H3PO4 and the action of heat. Despite these modifications, both the ATSCG and SCG spectra maintain similar profiles, indicating a functional composition that remains comparable between the materials.
On the other hand, the spectra of the biosorbents ACRFB, ATRFB, and BRFB exhibit significant changes in functional groups compared to LRFB (Figure 6B), which is attributed to the different treatments applied. In the region between 3600 and 3000 cm−1, the spectrum of LRFB shows a broad band attributed to the stretching vibrations of the O-H bond, characteristic of alcohols, phenols, carboxylic acids, and residual water [33]. This band disappears in ACRFB, ATRFB, and BRFB, probably due to the degradation of hydroxylated and volatile compounds resulting from the combination of H3PO4 and heat. Additionally, a reduction in intensity was observed in the region from 3000 to 2500 cm−1 associated with C–H bond vibrations [34], indicating the degradation of organic matter, such as lipids and lateral structures of lignin present in raw biomass, due to the treatments applied.
Interestingly, a weak band around 2165 cm−1 stands out in the adsorption spectra of SCG (Figure 6A), LRFB (Figure 6B), and their derivatives, attributed to the presence of cumulative bonds of the type C≡C or C≡N, as described by Chouchane et al. [53]. The persistence of this band, even after thermal and chemical treatments, suggests that unsaturated structures or stable aromatic compounds remain in the adsorbent’s structure, possibly originating from residues of coffee roasting.
Between 2000 and 1500 cm−1, characteristic bands of C=O bonds in carbonyl groups are observed [54]. These bands are more prominent in the LRFB and ATRFB spectra, indicating a higher presence of oxygenated compounds. In contrast, in the ACRFB and BRFB spectra, there is a notable reduction in the intensity of these bands, suggesting thermal degradation and more efficient removal of oxygenated groups during activation processes with H3PO4 and pyrolysis.
In the range between 1000 and 500 cm−1, bands associated with out-of-plane vibrations of aromatic rings and deformations of C–N and C–H bonds are present [36]. The widespread decrease in the intensity of these bands in the ACSCG and ACRFB spectra supports the idea that activation processes caused significant structural changes, which then led to the removal of organic fractions and functional groups from the original matrix.

3.7. Adsorption Efficiency of Dyes Remazol by Biosorbents

Table 4 presents the results of the adsorption assay for removing textile dyes (Remazol Yellow, Black, and Red) using CAC and various biosorbents, highlighting the impact of the physicochemical treatments applied to the waste-based raw materials (SCG and RFB).
It is observed that the ACSCG presents a removal efficiency very close to that of the CAC for all the dyes evaluated, achieving about 98–99% removal. These results corroborate the studies of Ismanto et al. [55], which highlight the viability of using SCG as an efficient adsorbent material for dye removal, thus promoting the valorization of a previously neglected waste.
ACRFB also demonstrated remarkable performance, especially in the adsorption of the Remazol Yellow (99.02 mg/L), a value higher than that obtained by CAC (98.17 mg/L) and ACSCG (98.78 mg/L). Although its efficiency for adsorbing Remazol Black (62.18 mg/L) and Remazol Red (68.01 mg/L) was lower than that of CAC and ACSCG, the results were still significantly higher than those obtained by the biochars (BSCG and BRFB).
Kim et al. [56] obtained similar results using the Escherichia coli waste biomass as a biosorbent for Reactive Yellow 2 (RY2). This indicates that utilizing the resulting biomass from fermentative processes as an adsorptive material represents a sustainable and economically viable strategy for wastewater treatment. In addition to reducing the operational and environmental costs associated with the disposal of these waste materials, this approach contributes to the circular economy by promoting the reuse of industrial by-products and mitigating environmental impacts. Thus, the use of residual biomass as an adsorbent combines technological innovation with environmental preservation, being a promising alternative for the development of cleaner and more efficient processes [57].
On the other hand, ATSCG demonstrated excellent performance for Remazol Yellow (98.22 mg/L), but its efficiency drops for the black (43.48 mg/L) and red (78.83 mg/L) dyes. These results suggest that acidic treatment promotes the formation of functional groups that interact more effectively with various types of dyes. In contrast, ATRFB showed the poorest overall performance among the treated adsorbents. This suggests that acid treatment alone is insufficient to impart the relevant properties to the RFB.
The natural or only freeze-dried adsorbents, namely SCG and LRFB, exhibited low adsorption capacities, particularly in the removal of Remazol Red, with values of 4.95 mg/L and 0.00 mg/L, respectively. These results indicate that the direct application of these waste materials without thermal or chemical treatment severely limits their effectiveness as adsorbents. There is a need for thermal or chemical treatments to increase the adsorption capacity of these waste materials. In general, the data reinforce the importance of carbonization and chemical/thermal activation processes in transforming organic waste, such as SCG and RFB, into high-performance adsorbents for removing recalcitrant textile dyes from aqueous solutions.
Since the best dye adsorption results were verified for the activated carbons used (CAC, ACSCG, and ACRFB), they were subjected to FTIR spectroscopic analysis before and after the adsorption test. The spectra in Figure 7 reveal noticeable structural modifications in each adsorbent, indicating interactions between surface functional groups and dye molecules. These interactions directly influenced adsorption efficiency, as demonstrated by the data presented in Table 4.
For CAC (Figure 7A), a discreet change in the bands’ intensity is observed across the broad region from 4000 to 500 cm−1 in the spectra of the sorbent after removing the three dyes evaluated. This indicates that its adsorption predominantly occurs through physical mechanisms. For the Remazol Yellow and Black dyes, partial interactions with the functional groups on the CAC surface are detected. However, for Remazol Red, more pronounced changes are evident, including a significant decrease in transmittance in several ranges (especially below 1000 cm−1, such as at 631.96, 534.28, and 448.11 cm−1), as well as shifts in the bands related to C≡C and C≡N bonds. These findings suggest the occurrence of stronger chemical interactions with the functional groups of the dye. According to Campbell et al. [50], this is probably because the CAC is highly carbonized and presents few functional groups. Although this mechanism limits its selectivity, it maintains high overall efficiency, as demonstrated in Table 4.
Regarding the spectra of ACSCG (Figure 7B), more pronounced changes are observed after the adsorption of the three dyes, especially in the bands around 2920/2850 cm−1 (aliphatic C–H), 1700 cm−1 (C=O, carbonyls), and 300–1000 cm−1 (C–O of alcohols or phenols). These changes indicate the active participation of the residual oxygenated groups on the adsorbent surface, which remain even after the chemical activation process. The adsorption process is likely mediated by hydrogen bonds and electrostatic interactions between the functional groups of the dye molecules and the active sites on the ACSCG surface. This combination of chemical functionality and a porous structure explains the excellent performance of the ACSCG, with removal efficiencies comparable to or exceeding those of CAC, as shown in Table 4.
In the case of ACRFB (Figure 7C), the spectra of this biosorbent after removing Remazol Yellow and Black show a moderate decrease in the intensity of the bands between 1400 and 1000 cm−1, indicating the involvement of C–O groups in the adsorption process. Additionally, a reduction in the band at 2889 cm−1 (aliphatic C–H) suggests that aliphatic chains are also involved. These findings indicate that the adsorption of both dyes mainly occurred through specific chemical interactions, with Remazol Yellow also being affected by physical mechanisms, such as pore entrapment. This may explain its higher removal efficiency compared to CAC.
Figure 7C also shows the spectrum of ACRFB after removing Remazol Red, which exhibits more intense and broader changes, especially in the regions associated with C–H and C–O bonds, indicating a strong chemical interaction with the biosorbent surface. However, the experimental results show a low removal efficiency (Table 4), indicating that although there is some chemical affinity, the physical interaction (such as diffusion and retention in the pores) was insufficient, possibly due to the incompatibility between the size of the dye molecule and the porous structure of the adsorbent. Lucaci et al. [58] stated that the biosorption performance of adsorbents is not limited to their surface area and porosity; it is also influenced by the number and nature of the functional groups present on their surface.
Although bioadsorbents have demonstrated high efficiency in removing Remazol dyes, their potential for reuse and regeneration has not been evaluated in this study. Future work should include adsorption–desorption cycle tests to assess their long-term applicability in wastewater treatment.

4. Conclusions

The results of this study demonstrate the viability of SCG as a sustainable and efficient substrate for laccase production through SSF using Lentinus crinitus UCP 1206. The optimized conditions, namely a particularly low substrate amount and high moisture, significantly enhanced enzymatic activity. Structural and chemical modifications confirmed via FTIR and SEM support the bioconversion of SCG during fermentation. Furthermore, SCG and RFB, when subjected to chemical activation, exhibited high adsorption capacity for textile dyes, showing performance comparable to that of CAC. These findings not only highlight the dual application potential of SCG in enzyme production and environmental remediation but also reinforce the importance of integrating agro-industrial residues into circular biorefinery models. Future studies may focus on scaling the process and evaluating other ligninolytic enzymes and pollutant classes to broaden the application of these biosorbents.

Author Contributions

E.d.S.F.: Conceptualization, formal analysis, investigation, methodology, writing—original draft, writing—review and editing. A.F.d.S., D.M.R., N.Z.d.P., A.G.D.N. and K.B.B.C.: investigation, methodology, writing—original draft. G.M.d.C.-T.: conceptualization, resources, validation, visualization. M.A.B.d.L. and A.L.F.P.: conception, funding, resources, supervision, validation, visualization, writing—original draft, writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by FACEPE (Foundation for the Support of Science and Technology of Pernambuco), grant number IBPG-1590-2.00/21, CNPq (National Council for Scientific and Technological Development), grant numbers GMCT Process Nr. 312242/2022-4 and ALFP Process Nr. 308824/2022-9.

Data Availability Statement

All data sets are available upon request.

Acknowledgments

The authors would like to thank the Multiuser Center for Analysis and Characterization of Biomolecules and Surface Materials (CEMACBIOS) at the Catholic University of Pernambuco for the use of its laboratories, and the Analytical Center of the Department of Chemistry at the Federal University of Pernambuco for the use of its chemical analysis equipment.

Conflicts of Interest

The authors declare no conflict of interest.

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Fermentation 11 00396 g001
Figure 1. Pareto chart of standardized effects of SCG amount, moisture, and temperature on the activity of laccase produced by Lentinus crinitus UCP 1206 in SSF.
Figure 1. Pareto chart of standardized effects of SCG amount, moisture, and temperature on the activity of laccase produced by Lentinus crinitus UCP 1206 in SSF.
Fermentation 11 00396 g001
Fermentation 11 00396 g002
Figure 2. Response surface of the activity of laccase produced by Lentinus crinitus UCP 1206 in SSF.
Figure 2. Response surface of the activity of laccase produced by Lentinus crinitus UCP 1206 in SSF.
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Fermentation 11 00396 g003
Figure 3. Infrared absorption spectrum of SCG before and after fermentation processes (SSF and SmF) by L. crinitus UCP 1206.
Figure 3. Infrared absorption spectrum of SCG before and after fermentation processes (SSF and SmF) by L. crinitus UCP 1206.
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Fermentation 11 00396 g004
Figure 4. Surface morphology of spent coffee grounds (SCG) particles observed by SEM before and after fermentation by L. crinitus UCP 1206. SCG before fermentation processes (A,B), after SmF (C,D), and after SSF (E,F). (A,C,E ×190 and B,D,F ×500).
Figure 4. Surface morphology of spent coffee grounds (SCG) particles observed by SEM before and after fermentation by L. crinitus UCP 1206. SCG before fermentation processes (A,B), after SmF (C,D), and after SSF (E,F). (A,C,E ×190 and B,D,F ×500).
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Fermentation 11 00396 g005
Figure 5. Effect of pH and temperature on activity and stability of laccase produced by L. crinitus UCP 1206 in SSF. Evaluation of laccase activity at different pHs (A) and temperatures (B); stability of laccase activity at different pHs (C) and temperatures (D).
Figure 5. Effect of pH and temperature on activity and stability of laccase produced by L. crinitus UCP 1206 in SSF. Evaluation of laccase activity at different pHs (A) and temperatures (B); stability of laccase activity at different pHs (C) and temperatures (D).
Fermentation 11 00396 g005
Fermentation 11 00396 g006
Figure 6. FTIR spectra of the different adsorbents used in this study. (A) Spectra of commercial activated carbon (CAC) and the biosorbents based on spent coffee grounds (SCG): SCG, activated carbon from SCG (ACSCG), acid-treated SCG (ATSCG), and biochar of SCG (BSCG). (B) Spectra of biosorbents based on the resulting fermented biomass (RFB): lyophilized RFB (LRFB), activated carbon from RFB (ACRFB), acid-treated RFB (ATRFB), and biochar of RFB (BRFB).
Figure 6. FTIR spectra of the different adsorbents used in this study. (A) Spectra of commercial activated carbon (CAC) and the biosorbents based on spent coffee grounds (SCG): SCG, activated carbon from SCG (ACSCG), acid-treated SCG (ATSCG), and biochar of SCG (BSCG). (B) Spectra of biosorbents based on the resulting fermented biomass (RFB): lyophilized RFB (LRFB), activated carbon from RFB (ACRFB), acid-treated RFB (ATRFB), and biochar of RFB (BRFB).
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Fermentation 11 00396 g007
Figure 7. FTIR spectra of activated carbons before and after the adsorption of the Remazol Yellow, Black, and Red dyes. (A) Commercial activated carbon—CAC; (B) activated carbon from spent coffee grounds—ACSCG; (C) activated carbon from the resulting fermented biomass—ACRFB.
Figure 7. FTIR spectra of activated carbons before and after the adsorption of the Remazol Yellow, Black, and Red dyes. (A) Commercial activated carbon—CAC; (B) activated carbon from spent coffee grounds—ACSCG; (C) activated carbon from the resulting fermented biomass—ACRFB.
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Table 1. Variables and levels used in the 23 full-factorial design applied to investigate laccase production using SCG as a substrate in SSF.
Table 1. Variables and levels used in the 23 full-factorial design applied to investigate laccase production using SCG as a substrate in SSF.
VariablesLevels
−10+1
SCG amount (g)51015
Moisture (%)406080
Temperature (°C)262830
Table 2. Comparison of laccase production by white-rot fungi using agro-industrial waste in solid-state fermentation.
Table 2. Comparison of laccase production by white-rot fungi using agro-industrial waste in solid-state fermentation.
FungiAgro-Industrial WastesFermentation Time (Days)Laccase Activity (U/g)References
L. crinitus UCP 1206Spent coffee grounds1514.62Present study
Phanerochaete chrysosporium MUCL 19343Brewery spent grain70.008[25]
Trametes versicolor + P. chrysosporiumCotton stalk
Wheat straw
Paddy straw		158.10
6.75
5.55		[26]
L. edodes Han 1788Cottonseed shell145.65[27]
Leaf of corncob114.46
Corncob132.31
T. versicolorTea residues76.40[28]
P. eryngiiCherry waste150.04[29]
T. versicolorBrewery spent grain70.78[30]
Pleurotus ostreatusPotato peel waste171.60[31]
Table 3. Full-factorial design applied to the production of laccase by Lentinus crinitus UCP 1206 using SCG as a sustainable substrate in SSF.
Table 3. Full-factorial design applied to the production of laccase by Lentinus crinitus UCP 1206 using SCG as a sustainable substrate in SSF.
AssaysSCG Amount (g)Moisture (%)Temperature (°C)Laccase Activity (U/g)
1540267.38
21540260.16
35802620.64
41580267.05
5540309.88
61540304.83
75803023.78
81580308.80
910602814.41
1010602812.73
1110602815.35
1210602813.44
Table 4. Efficiency of the biosorbents evaluated in the adsorption of the Remazol dyes (yellow, black, and red).
Table 4. Efficiency of the biosorbents evaluated in the adsorption of the Remazol dyes (yellow, black, and red).
BiosorbentsDye Adsorption (mg/L)
Remazol YellowRemazol BlackRemazol Red
CAC98.17 ± 0.0199.27 ± 0.0196.94 ± 0.03
SCG25.08 ± 0.0119.24 ± 0.024.95 ± 0.00
ACSCG98.78 ± 0.0099.13 ± 0.0198.34 ± 0.01
ATSCG98.22 ± 0.0043.48 ± 0.0278.83 ± 0.00
BSCG40.39 ± 0.0449.68 ± 0.0627.91 ± 0.02
LRFB26.92 ± 0.0214.34 ± 0.0416.34 ± 0.03
ACRFB99.02 ± 0.0062.18 ± 0.0568.01 ± 0.00
ATRFB14.70 ± 0.000.00 ± 0.0414.50± 0.00
BRFB48.35 ± 0.0562.18 ± 0.060.00 ± 0.04
CAC—commercial activated carbon; SCG—spent coffee grounds (untreated and unfermented); ACSCG—activated carbon from SCG; ATSCG—acid-treated SCG; BSCG—biochar of SCG; LRFB—lyophilized resulting fermented biomass (untreated); ACRFB—activated carbon from RFB; ATRFB—acid-treated RFB; BRFB—biochar of RFB.
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MDPI and ACS Style

França, E.d.S.; de Souza, A.F.; Rodríguez, D.M.; de Paula, N.Z.; Neves, A.G.D.; Cardoso, K.B.B.; Campos-Takaki, G.M.d.; de Lima, M.A.B.; Porto, A.L.F. Valorization of Spent Coffee Grounds as a Substrate for Fungal Laccase Production and Biosorbents for Textile Dye Decolorization. Fermentation 2025, 11, 396. https://doi.org/10.3390/fermentation11070396

AMA Style

França EdS, de Souza AF, Rodríguez DM, de Paula NZ, Neves AGD, Cardoso KBB, Campos-Takaki GMd, de Lima MAB, Porto ALF. Valorization of Spent Coffee Grounds as a Substrate for Fungal Laccase Production and Biosorbents for Textile Dye Decolorization. Fermentation. 2025; 11(7):396. https://doi.org/10.3390/fermentation11070396

Chicago/Turabian Style

França, Eduardo da Silva, Adriana Ferreira de Souza, Dayana Montero Rodríguez, Nazareth Zimiani de Paula, Anna Gabrielly Duarte Neves, Kethylen Barbara Barbosa Cardoso, Galba Maria de Campos-Takaki, Marcos Antonio Barbosa de Lima, and Ana Lucia Figueiredo Porto. 2025. "Valorization of Spent Coffee Grounds as a Substrate for Fungal Laccase Production and Biosorbents for Textile Dye Decolorization" Fermentation 11, no. 7: 396. https://doi.org/10.3390/fermentation11070396

APA Style

França, E. d. S., de Souza, A. F., Rodríguez, D. M., de Paula, N. Z., Neves, A. G. D., Cardoso, K. B. B., Campos-Takaki, G. M. d., de Lima, M. A. B., & Porto, A. L. F. (2025). Valorization of Spent Coffee Grounds as a Substrate for Fungal Laccase Production and Biosorbents for Textile Dye Decolorization. Fermentation, 11(7), 396. https://doi.org/10.3390/fermentation11070396

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