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Novel Biochemical Processes for Treatment and Valorization of Wastes and Biomass

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Green Chemistry".

Deadline for manuscript submissions: closed (30 November 2024) | Viewed by 16124

Special Issue Editor


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Guest Editor
Department of Sustainable Agriculture, University of Patras, 2 Georgiou Seferi St., Agrinio, Greece
Interests: microbial fuel cells (MFCs); microbial electrolysis cells (MECs); biofuel production via microbial processes (anaerobic digestion, fermentative hydrogen production and bioethanol production)
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Special Issue Information

Dear Colleagues,

Biochemical processes offer various possibilities for biomass treatment and valorization toward the production of energy, biofuels, and other bio-based products. These processes are generally considered to be environmentally friendly, operating under mild conditions of temperature and pressure and with a small amount of chemical additives. Biological processes imply the use of enzymes and microorganisms, with the former used as pure or mixed microbial consortia, under aerobic or anaerobic conditions. Wastes, energy crops, industrial wastewaters, and residual biomass are the target feedstocks for sustainable biochemical processing and the production of valuable molecules and compounds via cost-effective roots.

This Special Issue aims to gather recent developments on the treatment and valorization of wastes and biomass for the generation of bioenergy, biofuels, and high-added-value biobased materials. The Special Issue aspires to expand the knowledge in the field of biochemical technology, presenting original innovative research, including but not limited to 1) new feedstocks and 2) novel biocatalysts for the treatment and valorization of wastes and biomass, 3) innovative biochemical approaches for waste and biomass conversion, and 4) life cycle analysis and technoeconomical evaluation of waste and biomass biochemical processing.

Dr. Georgia Antonopoulou
Guest Editor

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Keywords

  • waste/biomass
  • valorization
  • biochemical processing
  • feedstocks
  • biocatalysts
  • life cycle analysis
  • biochemical approach

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Published Papers (10 papers)

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Research

23 pages, 6083 KiB  
Article
Studies on the Enzymatic Degradation Process of Epoxy-Polyurethane Compositions Obtained with Raw Materials of Natural Origin
by Anna Sienkiewicz and Piotr Czub
Molecules 2024, 29(23), 5667; https://doi.org/10.3390/molecules29235667 - 29 Nov 2024
Viewed by 258
Abstract
Along with the development of technology and the increasing consumption of polymeric materials, which have become an integral part of man’s everyday life, problems related to their disposal are arising. The presented research concentrates on the studies on the enzymatic degradation of selected [...] Read more.
Along with the development of technology and the increasing consumption of polymeric materials, which have become an integral part of man’s everyday life, problems related to their disposal are arising. The presented research concentrates on the studies on the enzymatic degradation of selected epoxy-polyurethane materials filled with 2 or 5 wt.% of waste unmodified or chemically modified through mercerization wood flour. Composites, subjected to the degradation process, contained up to 60% of raw materials of natural origin. The enzymatic degradation was carried out for 28 days, in three environmental conditions, differing in the type of applied buffer, pH, process temperature, the amount, and the type of applied enzyme. In this study, the influence of two lipases was tested (specifically: lipase of microbiological origin—Rhizopus Oryzae Lipase, and one of animal origin—Porcine Pancreas Lipase). There were seven compositions tested, based on the polyaddition product of epoxidized soybean oil with bisphenol A, differing in the amount of filler and the type of modification to which wood flour was subjected before the application in the polymer composite. After enzymatic degradation, the greatest progress of biodegradation was observed at T = 30 °C, in a complex phosphate buffer with pH = 6.8, in the presence of the Porcine Pancreas enzyme. Under these conditions, a slightly smaller effect was also observed in the presence of the Rhizopus Oryzae enzyme. At the same time, the compositions containing mercerized wood flour turned out to be the most susceptible to biodegradation with the above-mentioned enzymes. After conducting the process in the full 4-week cycle numerous changes were noticed within the tested sample, such as (1) 7.0 %wt. of the overall weight loss of samples, (2) reducing the value of the static contact angle (e.g., from 116.7° before degradation to 27.2° at the end of the study), and (3) morphological appearance of the sample (sample’s surface had suffered erosion noticed as smoothest roughnesses and numerous empty holes throughout its entire volume), concerning sample’s condition before enzymatic degradation. Full article
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12 pages, 1030 KiB  
Article
Influence of Hydrogen and Ethanol Addition in Methanogen-Free Mixed Culture Syngas Fermentations in Trickle Bed Reactors
by Cesar Quintela, Iulian-Gabriel Alexe, Yvonne Nygård, Lisbeth Olsson, Ioannis V. Skiadas and Hariklia N. Gavala
Molecules 2024, 29(23), 5653; https://doi.org/10.3390/molecules29235653 - 29 Nov 2024
Viewed by 345
Abstract
The use of mixed cultures in gas fermentations could reduce operating costs in the production of liquid chemicals such as alcohols or carboxylic acids. However, directing reducing equivalents towards the desired products presents the challenge of co-existing competing pathways. In this study, two [...] Read more.
The use of mixed cultures in gas fermentations could reduce operating costs in the production of liquid chemicals such as alcohols or carboxylic acids. However, directing reducing equivalents towards the desired products presents the challenge of co-existing competing pathways. In this study, two trickle bed reactors were operated at acetogenic and chain elongating conditions to explore the fate of electron equivalents (ethanol, H2, and CO) and test pH oscillations as a strategy to target chain-elongated products. Hereby, the use of a H2-rich syngas increased gas conversion rates and the specificity towards acetic acid (86% of C-mol production, 9.0 g LEBV−1 day−1, with EBV referring to empty bed volume), while preliminary experiments with CO-rich syngas show promising results in increasing the ethanol production necessary to target chain-elongated products. On the other hand, ethanol supplementation hindered the endogenous ethanol production of the acetogenic culture but promoted butanol production (1.0 g LEBV−1 day−1) at high ethanol concentrations (9.6 g L−1) in the fresh media. Finally, pH oscillations improved chain elongation yields but negatively affected acetogenic growth, reducing production rates. Full article
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16 pages, 2414 KiB  
Article
Using Extracted Sugars from Spoiled Date Fruits as a Sustainable Feedstock for Ethanol Production by New Yeast Isolates
by Georgia Antonopoulou, Maria Kamilari, Dimitra Georgopoulou and Ioanna Ntaikou
Molecules 2024, 29(16), 3816; https://doi.org/10.3390/molecules29163816 - 11 Aug 2024
Viewed by 1174
Abstract
This study focuses on investigating sugar recovery from spoiled date fruits (SDF) for sustainable ethanol production using newly isolated yeasts. Upon their isolation from different food products, yeast strains were identified through PCR amplification of the D1/D2 region and subsequent comparison with the [...] Read more.
This study focuses on investigating sugar recovery from spoiled date fruits (SDF) for sustainable ethanol production using newly isolated yeasts. Upon their isolation from different food products, yeast strains were identified through PCR amplification of the D1/D2 region and subsequent comparison with the GenBank database, confirming isolates KKU30, KKU32, and KKU33 as Saccharomyces cerevisiae; KKU21 as Zygosaccharomyces rouxii; and KKU35m as Meyerozyma guilliermondii. Optimization of sugar extraction from SDF pulp employed response surface methodology (RSM), varying solid loading (20–40%), temperature (20–40 °C), and extraction time (10–30 min). Linear models for sugar concentration (R1) and extraction efficiency (R2) showed relatively high R2 values, indicating a good model fit. Statistical analysis revealed significant effects of temperature and extraction time on extraction efficiency. The results of batch ethanol production from SDF extracts using mono-cultures indicated varying consumption rates of sugars, biomass production, and ethanol yields among strains. Notably, S. cerevisiae strains exhibited rapid sugar consumption and high ethanol productivity, outperforming Z. rouxii and M. guilliermondii, and they were selected for scaling up the process at fed-batch mode in a co-culture. Co-cultivation resulted in complete sugar consumption and higher ethanol yields compared to mono-cultures, whereas the ethanol titer reached 46.8 ± 0.2 g/L. Full article
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18 pages, 6961 KiB  
Article
Obtention and Characterization of Microcrystalline Cellulose from Industrial Melon Residues Following a Biorefinery Approach
by Ricardo Gómez-García, Sérgio C. Sousa, Óscar L. Ramos, Débora A. Campos, Cristóbal N. Aguilar, Ana R. Madureira and Manuela Pintado
Molecules 2024, 29(14), 3285; https://doi.org/10.3390/molecules29143285 - 11 Jul 2024
Viewed by 1112
Abstract
Residual melon by-products were explored for the first time as a bioresource of microcrystalline cellulose (MCC) obtention. Two alkaline extraction methods were employed, the traditional (4.5% NaOH, 2 h, 80 °C) and a thermo-alkaline in the autoclave (2% NaOH, 1 h, 100 °C), [...] Read more.
Residual melon by-products were explored for the first time as a bioresource of microcrystalline cellulose (MCC) obtention. Two alkaline extraction methods were employed, the traditional (4.5% NaOH, 2 h, 80 °C) and a thermo-alkaline in the autoclave (2% NaOH, 1 h, 100 °C), obtaining a yield of MCC ranging from 4.76 to 9.15% and 2.32 to 3.29%, respectively. The final MCCs were characterized for their chemical groups by Fourier-transform infrared spectroscopy (FTIR), crystallinity with X-ray diffraction, and morphology analyzed by scanning electron microscope (SEM). FTIR spectra showed that the traditional protocol allows for a more effective hemicellulose and lignin removal from the melon residues than the thermo-alkaline process. The degree of crystallinity of MCC ranged from 51.51 to 61.94% and 54.80 to 55.07% for the thermo-alkaline and traditional processes, respectively. The peaks detected in X-ray diffraction patterns indicated the presence of Type I cellulose. SEM analysis revealed microcrystals with rough surfaces and great porosity, which could remark their high-water absorption capacity and drug-carrier capacities. Thus, these findings could respond to the need to valorize industrial melon by-products as raw materials for MCC obtention with potential applications as biodegradable materials. Full article
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21 pages, 3602 KiB  
Article
Enhancement of Biodegradability of Chicken Manure via the Addition of Zeolite in a Two-Stage Dry Anaerobic Digestion Configuration
by Achilleas Kalogiannis, Ioanna A. Vasiliadou, Athanasios Tsiamis, Ioannis Galiatsatos, Panagiota Stathopoulou, George Tsiamis and Katerina Stamatelatou
Molecules 2024, 29(11), 2568; https://doi.org/10.3390/molecules29112568 - 30 May 2024
Cited by 1 | Viewed by 763
Abstract
Leach bed reactors (LBRs) are dry anaerobic systems that can handle feedstocks with high solid content, like chicken manure, with minimal water addition. In this study, the chicken manure was mixed with zeolite, a novel addition, and packed in the LBR to improve [...] Read more.
Leach bed reactors (LBRs) are dry anaerobic systems that can handle feedstocks with high solid content, like chicken manure, with minimal water addition. In this study, the chicken manure was mixed with zeolite, a novel addition, and packed in the LBR to improve biogas production. The resulting leachate was then processed in a continuous stirred tank reactor (CSTR), where most of the methane was produced. The supernatant of the CSTR was returned to the LBR. The batch mode operation of the LBR led to a varying methane production rate (MPR) with a peak in the beginning of each batch cycle when the leachate was rich in organic matter. Comparing the MPR in both systems, the peaks in the zeolite system were higher and more acute than in the control system, which was under stress, as indicated by the acetate accumulation at 2328 mg L−1. Moreover, the presence of zeolite in the LBR played a crucial role, increasing the overall methane yield from 0.142 (control experiment) to 0.171 NL CH4 per g of volatile solids of chicken manure entering the system at a solid retention time of 14 d. Zeolite also improved the stability of the system. The ammonia concentration increased gradually due to the little water entering the system and reached 3220 mg L−1 (control system) and 2730 mg L−1 (zeolite system) at the end of the experiment. It seems that zeolite favored the accumulation of the ammonia at a lower rate (14.0 mg L−1 d−1) compared to the control experiment (17.3 mg L−1 d−1). The microbial analysis of the CSTR fed on the leachate from the LBR amended with zeolite showed a higher relative abundance of Methanosaeta (83.6%) compared to the control experiment (69.1%). Both CSTRs established significantly different bacterial profiles from the inoculum after 120 days of operation (p < 0.05). Regarding the archaeal communities, there were no significant statistical differences between the CSTRs and the inoculum (p > 0.05). Full article
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12 pages, 3331 KiB  
Article
Synthesis of a Grease Thickener from Cashew Nut Shell Liquor
by Son A. Hoang, Khanh D. Pham, Nhung H. Nguyen, Ha T. Tran, Ngoc Hoang and Chi M. Phan
Molecules 2023, 28(22), 7624; https://doi.org/10.3390/molecules28227624 - 16 Nov 2023
Viewed by 1408
Abstract
Thickener, also known as a gelling agent, is a critical component of lubricating greases. The most critical property of thickener, temperature resistance, is determined by the molecular structure of the compounds. Currently, all high-temperature-resistant thickeners are based on 12-hydroxystearic acid, which is exclusively [...] Read more.
Thickener, also known as a gelling agent, is a critical component of lubricating greases. The most critical property of thickener, temperature resistance, is determined by the molecular structure of the compounds. Currently, all high-temperature-resistant thickeners are based on 12-hydroxystearic acid, which is exclusively produced from castor oil. Since castor oil is also an important reagent for other processes, finding a sustainable alternative to 12-hydroxystearic acid has significant economic implications. This study synthesises an alternative thickener from abundant agricultural waste, cashew nut shell liquor (CNSL). The synthesis and separation procedure contains three steps: (i) forming and separating calcium anacardate by precipitation, (ii) forming and separating anacardic acid (iii) forming lithium anacardate. The obtained lithium anacardate can be used as a thickener for lubricating grease. It was found that the recovery of anacardic acid was around 80%. The optimal reaction temperature and time conditions for lithium anacardate were 100 °C and 1 h, respectively. The method provides an economical alternative to castor and other vegetable oils. The procedure presents a simple pathway to produce the precursor for the lubricating grease from agricultural waste. The first reaction step can be combined with the existing distillation of cashew nut shell processing. An effective application can promote CNSL to a sustainable feedstock for green chemistry. The process can also be combined with recycled lithium from the spent batteries to improve the sustainability of the battery industry. Full article
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12 pages, 2804 KiB  
Article
An Alternative Exploitation of Synechocystis sp. PCC6803: A Cascade Approach for the Recovery of High Added-Value Products
by Paola Imbimbo, Luigi D’Elia, Iolanda Corrado, Gerardo Alvarez-Rivera, Antonio Marzocchella, Elena Ibáñez, Cinzia Pezzella, Filipe Branco dos Santos and Daria Maria Monti
Molecules 2023, 28(7), 3144; https://doi.org/10.3390/molecules28073144 - 31 Mar 2023
Cited by 3 | Viewed by 2977
Abstract
Microalgal biomass represents a very interesting biological feedstock to be converted into several high-value products in a biorefinery approach. In this study, the cyanobacterium Synechocystis sp. PCC6803 was used to obtain different classes of molecules: proteins, carotenoids and lipids by using a cascade [...] Read more.
Microalgal biomass represents a very interesting biological feedstock to be converted into several high-value products in a biorefinery approach. In this study, the cyanobacterium Synechocystis sp. PCC6803 was used to obtain different classes of molecules: proteins, carotenoids and lipids by using a cascade approach. In particular, the protein extract showed a selective cytotoxicity towards cancer cells, whereas carotenoids were found to be active as antioxidants both in vitro and on a cell-based model. Finally, for the first time, lipids were recovered from Synechocystis biomass as the last class of molecules and were successfully used as an alternative substrate for the production of polyhydroxyalkanoate (PHA) by the native PHA producer Pseudomonas resinovorans. Taken together, our results lead to a significant increase in the valorization of Synechocystis sp. PCC6803 biomass, thus allowing a possible offsetting of the process costs. Full article
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17 pages, 2480 KiB  
Article
Microbial Enrichment Techniques on Syngas and CO2 Targeting Production of Higher Acids and Alcohols
by Styliani Konstantinidi, Ioannis V. Skiadas and Hariklia N. Gavala
Molecules 2023, 28(6), 2562; https://doi.org/10.3390/molecules28062562 - 11 Mar 2023
Cited by 1 | Viewed by 1856
Abstract
(1) Background: Microbial conversion of gaseous molecules, such as CO2, CO and H2, to valuable compounds, has come to the forefront since the beginning of the 21st century due to increasing environmental concerns and the necessity to develop alternative technologies [...] Read more.
(1) Background: Microbial conversion of gaseous molecules, such as CO2, CO and H2, to valuable compounds, has come to the forefront since the beginning of the 21st century due to increasing environmental concerns and the necessity to develop alternative technologies that contribute to a fast transition to a more sustainable era. Research efforts so far have focused on C1–C2 molecules, i.e., ethanol and methane, while interest in molecules with higher carbon atoms has also started to emerge. Research efforts have already started to pay off, and industrial installments on ethanol production from steel-mill off-gases as well as methane production from the CO2 generated in biogas plants are a reality. (2) Methodology: The present study addresses C4–C6 acids and butanol as target molecules and responds to how the inherent metabolic potential of mixed microbial consortia could be revealed and exploited based on the application of different enrichment methods (3) Results and Conclusions: In most of the enrichment series, the yield of C4–C6 acids was enhanced with supplementation of acetic acid and ethanol together with the gas substrates, resulting in a maximum of 43 and 68% (e-mol basis) for butyric and caproic acid, respectively. Butanol formation was also enhanced, to a lesser degree though and up to 9% (e-mol basis). Furthermore, the microbial community exhibited significant shifts depending on the enrichment conditions applied, implying that a more profound microbial analysis on the species level taxonomy combined with the development of minimal co-cultures could set the basis for discovering new microbial co-cultures and/or co-culturing schemes. Full article
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16 pages, 2238 KiB  
Article
Sugar Beet Pulp as a Biorefinery Substrate for Designing Feed
by Dawid Dygas, Dorota Kręgiel and Joanna Berłowska
Molecules 2023, 28(5), 2064; https://doi.org/10.3390/molecules28052064 - 22 Feb 2023
Cited by 8 | Viewed by 3612
Abstract
An example of the implementation of the principles of the circular economy is the use of sugar beet pulp as animal feed. Here, we investigate the possible use of yeast strains to enrich waste biomass in single-cell protein (SCP). The strains were evaluated [...] Read more.
An example of the implementation of the principles of the circular economy is the use of sugar beet pulp as animal feed. Here, we investigate the possible use of yeast strains to enrich waste biomass in single-cell protein (SCP). The strains were evaluated for yeast growth (pour plate method), protein increment (Kjeldahl method), assimilation of free amino nitrogen (FAN), and reduction of crude fiber content. All the tested strains were able to grow on hydrolyzed sugar beet pulp-based medium. The greatest increases in protein content were observed for Candida utilis LOCK0021 and Saccharomyces cerevisiae Ethanol Red (ΔN = 2.33%) on fresh sugar beet pulp, and for Scheffersomyces stipitis NCYC1541 (ΔN = 3.04%) on dried sugar beet pulp. All the strains assimilated FAN from the culture medium. The largest reductions in the crude fiber content of the biomass were recorded for Saccharomyces cerevisiae Ethanol Red (Δ = 10.89%) on fresh sugar beet pulp and Candida utilis LOCK0021 (Δ = 15.05%) on dried sugar beet pulp. The results show that sugar beet pulp provides an excellent matrix for SCP and feed production. Full article
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14 pages, 1600 KiB  
Article
Fermentative α-Humulene Production from Homogenized Grass Clippings as a Growth Medium
by Alexander Langsdorf, Anna-Lena Drommershausen, Marianne Volkmar, Roland Ulber and Dirk Holtmann
Molecules 2022, 27(24), 8684; https://doi.org/10.3390/molecules27248684 - 8 Dec 2022
Cited by 9 | Viewed by 1857
Abstract
Green waste, e.g., grass clippings, is currently insufficiently recycled and has untapped potential as a valuable resource. Our aim was to use juice from grass clippings as a growth medium for microorganisms. Herein, we demonstrate the production of the sesquiterpene α-humulene with the [...] Read more.
Green waste, e.g., grass clippings, is currently insufficiently recycled and has untapped potential as a valuable resource. Our aim was to use juice from grass clippings as a growth medium for microorganisms. Herein, we demonstrate the production of the sesquiterpene α-humulene with the versatile organism Cupriavidus necator pKR-hum on a growth medium from grass clippings. The medium was compared with established media in terms of microbial growth and terpene production. C. necator pKR-hum shows a maximum growth rate of 0.43 h−1 in the grass medium and 0.50 h−1 in a lysogeny broth (LB) medium. With the grass medium, 2 mg/L of α-humulene were produced compared to 10 mg/L with the LB medium. By concentrating the grass medium and using a controlled bioreactor in combination with an optimized in situ product removal, comparable product concentrations could likely be achieved. To the best of our knowledge, this is the first time that juice from grass clippings has been used as a growth medium without any further additives for microbial product synthesis. This use of green waste as a material represents a new bioeconomic utilization option of waste materials and could contribute to improving the economics of grass biorefineries. Full article
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