Search Results (141)

This study investigates the valorization of carrot discard, a carbohydrate-rich agricultural residue, for the production of 2,3-butanediol (2,3-BDO). The fermentation process was evaluated using two strains, Bacillus licheniformis DSM 8785 and Bacillus amyloliquefaciens DSM 7. Two process configurations were compared: separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). Additionally, to determine substrate and product inhibition thresholds, fermentation assays were conducted in semi-defined media with glucose concentrations ranging from 20 to 120 g/L. The SHF strategy proved more effective than the SSF configuration. Under the SHF configuration, B. amyloliquefaciens demonstrated superior performance, yielding 16.7 g/L of 2,3-BDO. In contrast, B. licheniformis was notable for its high capacity for acetoin synthesis, producing 24.2 g/L of acetoin in addition to 10.9 g/L of 2,3-BDO. Therefore, these findings demonstrate that carrot discard is a viable feedstock for the co-production of 2,3-BDO and acetoin. Full article

The textile industry generates millions of tons of waste annually, posing significant environmental challenges. Addressing this issue, our study explores a sustainable biotechnological approach to convert cotton textile waste into valuable bioproducts. We evaluated the potential of Corynebacterium glutamicum ATCC 21492 for the production of L-lysine and other amino acids using glucose derived from cotton textile waste. Two experimental strategies were implemented: Sequential Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF). In SHF, optimization of initial glucose concentration, temperature, and inoculum size led to the highest L-lysine concentration of 2.38 g/L under conditions of 45 g/L glucose, 35 °C, and 2% inoculum. The production of L-lysine, along with varying proportions of other amino acids such as alanine, threonine, methionine, and leucine, was significantly influenced by these parameters. In SSF, the highest L-lysine yield of 3.10 mg/g untreated cotton was achieved at 14% cotton loading, 7% enzyme dose, 35 °C, and 10% inoculum concentration, corresponding to an L-lysine concentration of 0.5 g/L. This reduced concentration, compared to SHF, is primarily attributed to limitations in cotton hydrolysis under the studied conditions. Nevertheless, C. glutamicum utilized alternative carbon sources present in the culture medium, leading to a diversified amino acid profile in the final product. These findings support the feasibility of textile waste bioconversion using C. glutamicum and highlight its potential as a sustainable platform for amino acid production, aligning with circular economy principles and contributing to the reduction of the textile industry’s environmental impact. Full article

This study developed a solid-state fermentation system based on Trichoderma harzianum, which significantly enhanced the nutritional value of distiller’s grain (DG) feed through a multi-stage synergistic treatment process. During the cellulase production phase, rice husk was used as an auxiliary material, and specific degradation of DGs was effectively enhanced. Through optimization using response surface methodology, the optimal enzyme production conditions were determined. The filter paper enzyme activity reached a peak of 1.45 U/gds (enzyme activity per gram of dry substrate) when the moisture content was 53%, the fermentation time was 3 days, and the Tween-80 dosage was 0.015 mL/g (dry weight basis). Under these conditions, the crude enzyme solution was used to hydrolyze DGs. Compared to original DGs, the content of reducing sugars increased by 10.75%. In the stage of protein production, segmented hydrolysis fermentation (SHF) and simultaneous saccharification fermentation (SSF) processes were employed using yeast. The results showed that SSF pathway showed better performance, and the true protein content reached 15.16% after 11 days, an increase of 41.5% compared to the control. Finally, through secondary fermentation regulated by Lactobacillus fermentum, the flavor of the feed was significantly improved. This study innovatively integrated bio-enzymatic hydrolysis and multi-strain synergistic fermentation technologies, providing a novel strategy for the efficient and sustainable production of protein feed based on DGs. Full article

This study aims to identify the best conditions for liquid hot water pretreatment (LHW) of sweet stalk sorghum and the optimization method using the response surface method (RSM) with varying parameters, including temperature, reaction time, and acid catalysts, to enhance the enzymatic hydrolysis of pretreated sweet stalk sorghum. This study presents a novel approach by optimizing LHW pretreatment using RSM to maximize the glucose yield and minimize sugar degradation, in contrast to the widely used method of sulfuric acid hydrolysis combined with SSF. The goal is to achieve the highest glucose yield for ethanol production under optimal conditions. The results show that after the LHW pretreatment under optimal conditions, the optimal actual values have the highest glucose yield of 91.09% in a solid fraction at a sulfuric acid catalyst concentration of 0.90% with a pretreatment temperature of 110 °C for 90 min. The results of the statistical analysis of the glucose yield show an R-squared value of 0.9964 or 99.64%, which is statistically significant. In addition, the optimized pretreatment conditions significantly improved the accessibility of the enzyme. Pretreatment for ethanol production in sweet stalk sorghum samples was carried out with an H₂SO₄ catalyst concentration of 0.90% using the SSF method with the yeast strain S. cerevisiae. The results show that during the fermentation period of 0–96 h, the maximum ethanol concentration of 23.1 g/L occurred at 72 h under 25 FPU/g substrate at pH 4.8 and decreased 72 h after fermentation. In conclusion, sweet stalk sorghum is a promising candidate for ethanol production due to its high glucose yield and efficient enzymatic hydrolysis, making it a viable alternative for biomass-based energy production. Full article

The enzymatic hydrolysis of lignocellulose is often hindered by the glucose-mediated inhibition of β-glucosidases, a major bottleneck in industrial cellulose degradation. Identifying novel glucose-tolerant β-glucosidases is essential for enhancing saccharification efficiency. In this study, we cloned and heterologously expressed a novel β-glucosidase, RpBgl8, from the termite Reticulitermes perilucifugus in Escherichia coli. Sequence and structural analyses classified RpBgl8 as a glycoside hydrolase family 1 enzyme. The purified enzyme exhibited optimal activity at 45 °C and pH 7.0, with broad stability across pH 4.0–8.0. Notably, RpBgl8 demonstrated high tolerance to lignocellulose-derived inhibitors and organic solvents, maintaining 100% activity in 15% ethanol. Furthermore, RpBgl8 exhibited outstanding glucose tolerance, retaining 100% activity at 2.5 M glucose and 82% activity at 4.0 M glucose—outperforming most previously reported β-glucosidases. A structural analysis revealed a narrow, hydrophobic substrate pocket, with residue F124 at the glycone-binding site critical for minimizing glucose accumulation. The F124W mutation significantly reduced glucose tolerance, confirming that hydrophobic interactions at the active site mitigate inhibition. These findings establish RpBgl8 as a promising candidate for high-solid biomass processing and simultaneous saccharification and fermentation applications, highlighting termites as underexplored sources of biocatalysts with unique industrial potential. Full article

Interest in the production of bioethanol from inedible biomass is growing worldwide because of its sustainable supply and lack of competition with food supplies. Candida krusei (also known as Pichia kudriavzevii or Issatchenkia orientalis) is one of the most suitable thermotolerant yeasts used in the simultaneous saccharification and fermentation process for bioethanol production. In the production of bioethanol from lignocellulosic biomass as a feedstock, various environmental conditions occur, and the stress tolerance capacity of C. krusei, especially its low pH and tolerance to inhibitors, limits its practical application. In this study, to select a suitable second-generation bioethanol-producing strain, the tolerance capacity of five available C. krusei strains (NBRC0584, NBRC0841, NBRC1162, NBRC1395 and NBRC1664) was characterized. Spot assay and growth experiment results showed that among the five C. krusei strains, C. krusei NBRC1664 showed superior tolerance capacity for low pH and inhibitors. Furthermore, this strain efficiently produced ethanol from glucose under low pH conditions with or without sulfate. A comparative analysis of the draft genome sequences suggested that Opy2, Sln1 and Cdc24 in the HOG pathway are conserved only in C. krusei NBRC1664, which may contribute to its superior tolerance to low pH levels. Moreover, amino acid sequence alignment showed that aldehyde dehydrogenase family proteins, which catalyze the degradation of cyclic aldehydes, are commonly conserved in C. krusei. In addition, the increased transcription levels in C. krusei NBRC1664 could play a role in its higher tolerance to inhibitors. These results suggest that C. krusei NBRC1664 is a more suitable strain for application in industrial processes for second-generation bioethanol production. Full article

Bioethanol is a renewable, environmentally-friendly biofuel conventionally produced through the alcoholic fermentation of sugary or starch-rich substrates by microorganisms, commonly Yeast Saccharomyces cerevisiae. Intermediates of industrial wheat flour wet milling processing to starch, such as A-starch and B-starch milk, are cost-effective, abundant, and non-seasonal feedstocks for bioethanol production. This study evaluates the bioethanol production from wheat A-starch and B-starch milk and mixtures of these two substrates in different ratios (1:3, 1:1, and 3:1) using two cold hydrolysis procedures at 65 °C: (i) simultaneous liquefaction and saccharification (SLS) followed by fermentation, and (ii) liquefaction by alpha-amylase followed by simultaneous saccharification and fermentation (SSF). The results demonstrated that SSF and SLS are equally efficient procedures for reaching a high ethanol yield of 53 g per 100 g of starch and 93% of starch conversion to ethanol for all investigated substrates. Lower levels of non-starch components in A-starch milk, which typically contribute to volatile by-product formation, allowed clear distillate profiles in terms of and lower content of aldehydes, methanol, and volatile acidity, enhancing ethanol distillate purity compared to B-starch milk. Mixing high-quality A-starch milk with low-cost B-starch milk enables higher ethanol yield, improved distillate quality, and energy savings for efficient industrial-scale applications. Full article

Succinic acid is applied in many chemical industries in which it can be produced through microbial fermentation using lignocellulosic biomasses. Mixed-waste office paper (MWOP) containing lignocellulosic fibers is enormously generated globally. MWOP is recycled into toilet paper and cardboard, but the recovery process is costly. The reuse of MWOP to alternatively produce succinic acid is highly attractive. In this study, pretreatment of MWOPs with 1% (v/v) H₂SO₄ at 121 °C for 20 min was found to be optimal. The optimal conditions for the enzymatic hydrolysis of H₂SO₄-pretreated MWOP (AP-MWOP) were at 50 °C, with cellulase loading at 80 PCU/g AP-MWOP. This resulted in the highest glucose (22.46 ± 0.15 g/L) and xylose (5.11 ± 0.32 g/L). Succinic acid production via separate hydrolysis and fermentation (SHF) by Escherichia coli KJ122 reached 28.19 ± 0.98 g/L (productivity of 1.17 ± 0.04 g/L/h). For simultaneous saccharification and fermentation (SSF), succinic acid was produced at 24.58 ± 2.32 g/L (productivity of 0.82 ± 0.07 g/L/h). Finally, succinic acid at 51.38 ± 4.05 g/L with yield and productivity of 0.75 ± 0.05 g/g and 1.07 ± 0.08 g/L/h was achieved via fed-batch pre-saccharified SSF. This study not only offers means to reuse MWOP for producing succinic acid but also provides insights for exploiting other wastes to high-value succinic acid, supporting environmental sustainability and zero-waste society. Full article

The integrated production of ethanol fuel through the simultaneous use of various by-products and waste materials is an intriguing concept, as it maximizes the raw material potential while addressing the challenge of managing waste biomass from different technological processes. The efficient utilization of lignocellulosic waste depends on employing a pretreatment method that enhances the susceptibility of structural polysaccharides to hydrolysis. The aim of the study was to assess the possibility of the simultaneous use of corn stillage biomass and beet molasses as raw materials for the production of ethanol fuel. The research focused on optimizing the process conditions for the acid pretreatment of stillage biomass and the enzymatic hydrolysis of cellulose and evaluating the effectiveness of two fermentation strategies: SHF (Separate Hydrolysis and Fermentation) and SSF (Simultaneous Saccharification and Fermentation). The highest hydrolysis susceptibility was observed in biomass pretreated with 2% v/v H₃PO₄ for 30 min at 121 °C. The maximum glucose concentration of about 12 g/L (hydrolysis efficiency about 35.5%) was achieved even with the lowest enzyme dose, i.e., 7.5 FPU per gram of biomass. The yeast also showed high fermentation activity in media prepared from stillage biomass and molasses, producing about 50 g/L of ethanol regardless of the fermentation strategy used. The complete fermentation of carbohydrates assimilated by yeast confirmed the complementarity of the two raw materials used to prepare fermentation media, emphasizing the high potential of the proposed technological solution for ethanol fuel production. Full article

Steam explosion (SE) is an effective lignocellulose pretreatment technology for second-generation L-lactic acid (L-LA) production. In this study, targeted to produce high-concentration L-LA from corn stover (CS), the fed-batch simultaneous saccharification and fermentation (SSF) of acidic, SE-pretreated CS was developed and demonstrated in a 5 L scale bioreactor under non-strict conditions (without detoxification and sterilization). The results indicated that the fed-batch SSF, with a simple pH control, realized a higher tolerance of the strains to the toxic by-products of hydrolysate, in comparison to the conventional sequential hydrolysis and fermentation (SHF), allowing for 153.8 g L⁻¹ of L-LA production, along with a productivity of 1.83 g L⁻¹ h⁻¹ in a system with a total of 40% (w/v) solid loading. The mass balance indicated that up to 449 kg of L-LA can be obtained from 1 t of dried CS. It exhibited obvious superiorities and laid down a solid foundation for the industrialization of second-generation L-LA production. Full article

The global transition to a sustainable bioeconomy requires the engagement of renewable and cost-effective substrates to obtain valuable bio-based products. Inulin-rich plant materials have promising applications in white biotechnology. This review evaluates the potential of converting inulin through an integrated biorefinery into high-value products by microbial fermentation. It describes the methods for raw biomass and inulin pretreatment, the possibilities of simultaneous saccharification and fermentation (SSF), and the use of wild-type and genetically modified microbial strains. The bioconversion of inulin enables the efficient synthesis of biofuels such as ethanol, butanol, and 2,3-butanediol and biochemicals such as lactic, citric, and poly-γ-glutamic acid. By analyzing the advances in inulin hydrolysis methods, microbial engineering, and bioprocess optimization approaches, this review highlights the broad applicability of inulin in the biorefinery context as a multifunctional, sustainable substrate, which contributes to the development of the circular economy. Full article

High-temperature fermentation (HTF) of ethanol can reduce costs of cooling, sterilization, and related equipment compared to the costs of general ethanol fermentation. To realize HTF, however, there are various issues to be considered, such as the fermentation temperature upper limit for ethanol-producing thermotolerant yeast, the size of a fermenter that does not require cooling, and the effective temperature for suppressing microbial contamination. This study focused on these issues and also on downstream processes that exploit the advantages of HTF at temperatures exceeding 40 °C. The permissible size of a fermenter without cooling was estimated by simulating heat generation and heat dissipation. Fermentation productivity at high temperatures when using the thermotolerant yeast Kluyveromyces marxianus and the inhibitory effect of high temperatures on the growth of contaminant microorganisms were examined. After fermentation, the recovery and concentration of ethanol were performed by reduced-pressure distillation (RPD) and membrane separation. These experiments demonstrate that efficient HTF can reduce the amount of saccharifying enzymes in simultaneous saccharification and fermentation and can shorten the transition time from the saccharification step to the fermentation step in separate saccharification and fermentation, that RPD at fermentation temperatures enables a smooth connection to the HTF step and can be performed with a relatively weak vacuum, and that membrane separation can reduce the running cost compared to the cost of general distillation on a compact scale. Full article

Life cycle assessment of a technology is the key to technological development in the context of sustainable development. Orchard waste has been identified as a potential source of bioplastics. The objective of this study was to conduct a life cycle assessment of two specific bioplastic materials, namely, L-polylactic acid (PLA) and poly(3-hydroxybutyrate) (PHB). Bioplastics, such as PLA acid and PHB, can be used as alternatives to conventional plastics due to their biodegradability and non-toxicity, both of which have the potential to replace conventional petroleum-based plastics. Polylactic acid was synthesized from orchard waste in a series of stages, including biomass processing, pretreatment for carbohydrate extraction, simultaneous saccharification and fermentation (SSF), and microwave polymerization. PHB, another biodegradable polymer, is produced by microorganisms through the fermentation of sugars obtained from the same biomass. Applied LCAs show that for PLA production, the stages having the greatest environmental impact are biomass processing, pretreatment, and the SSF process, and for PHB production, very energy-intensive stages significantly contributing to the environmental impacts are biomass processing and pretreatment stages. For both PLA and PHB, the initial stages of biomass processing and pretreatment are the most energy-intensive and significant contributors to CO₂ emissions. Full article

The bioconversion of lignocellulosic biomass, which are abundant and renewable resources, into liquid fuels and bulk chemicals is a promising solution to the current challenges of resource scarcity, energy crisis, and carbon emissions. Considering the separation of some end-products, it is necessary to firstly obtain a high concentration separated fermentable sugar solution, and then conduct fermentation. For this purpose, in this study, using acid catalyzed steam explosion pretreated corn stover (ACSE-CS) and corn cob residues (CCR) as cellulosic substrate, respectively, the batch feeding strategies and enzymatic hydrolysis conditions were investigated to achieve the efficient enzymatic hydrolysis at high solid loading. It was shown that the fermentable sugar solutions of 161.2 g/L and 205 g/L were obtained, respectively, by fed-batch enzymatic hydrolysis of ACSE-CS under 30% of final solid loading with 10 FPU/g DM of crude cellulase, and of CCR at 27% of final solid loading with 8 FPU/g DM of crude cellulase, which have the potential to be directly applied to the large-scale fermentation process without the need for concentration, and the conversion of glucan in ACSE-CS and CCR reached 80.9% and 87.6%, respectively, at 72 h of enzymatic hydrolysis. This study also applied the fed-batch simultaneous saccharification and co-fermentation process to effectively convert the two cellulosic substrates into ethanol, and the ethanol concentrations in fermentation broth reached 46.1 g/L and 72.8 g/L for ACSE-CS and CCR, respectively, at 144 h of fermentation. This study provides a valuable reference for the establishment of “sugar platform” based on lignocellulosic biomass and the production of cellulosic ethanol. Full article

The issue of managing waste bread is a global concern, with significant environmental and the economic implications. The utilisation of waste bread for bioethanol production, employing energy-saving technology, could prevent these consequences and reduce the consumption of traditionally used fossil fuels. The objective of this study was to evaluate the influence of the type of waste bread (wheat and wheat–rye sourdough) and the mash preparation method on the results of alcoholic fermentation and the concentration of selected congeners in the distillates. The highest fermentation efficiency (96% of theoretical) was achieved for both types of bread through the utilisation of the pressureless starch liberation method combined with simultaneous saccharification and fermentation. The separate saccharification of starch resulted in lower process efficiencies (from 85.75 to 88.60% of theoretical). The application of the native starch hydrolysis method (without starch activation) for the fermentation of wheat bread-based mashes exhibited a higher efficiency (87.85% of the theoretical) than that observed for the wheat–rye bread-based mash sample (83.74% of theoretical). All of the obtained spirit distillates exhibited a low concentration of methanol (≤300 mg/L alcohol 100% v/v) and comply with the requirements of the EU regulation for ethyl alcohol of agricultural origin (rectified spirit). Full article