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This study investigated the impact of humic acid (HA) on enzymatic pretreatment efficiency, focusing on sludge properties and HA molecular structure. The results showed that enzymatic pretreatment alleviates HA inhibition, improving hydrolysis efficiency. In the presence of HA, soluble proteins and polysaccharides in the enzyme-cocktail group reached 27.7 mg/L and 23.9 mg/L, 1.4 and 1.3 times higher than the blank group, respectively. The enzyme-cocktail group also had the highest soluble DNA concentration (19.4 mg/L) and the lowest viable cell proportion (69.3 %), indicating effective cell lysis. Enzyme-cocktail pretreatment reduced electrostatic repulsion, enhancing the mobility of extracellular organics. Enzyme interactions with HA released internal hydrolases and decreased amide groups on the HA surface, increasing the availability of biodegradable substrates. Overall, enzymatic pretreatment proves effective in mitigating HA-induced inhibition, thereby improving sludge biodegradation and enhancing carbon recovery in anaerobic fermentation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The asynchronous dosed protease and lysozyme combination pretreatment was proved to be effective in enhancing the anaerobic fermentation of waste activated sludge (WAS). However, humic acid (HA) in the sludge could interact with hydrolase and restrain the hydrolysis efficiency, thus inhibiting short-chain fatty acids (SCFAs) production. This study investigated the effectiveness and mechanism of enzymatic pretreatment against HA. Results showed that the enzyme cocktail method increased the extracellular bioavailable contents by 34 %, which raised SCFAs production by 89.69 % (1269.65 mg COD /L). The balanced ratio of hydrolysis and fermentation communities suggested that the small molecular organics generated by the hydrolysis community could be sufficiently utilized by fermentation communities. The metabolism of amino acids and glucose was facilitated, and the activities of key enzymes were enhanced. These results clarified the effect of asynchronous enzyme cocktail pretreatment against HA inhibition and contributed to SCFAs production, which offered fresh perspectives on carbon recovery., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Anaerobic co-fermentation of swine manure (SM) and apple waste (AW) restricts by the slow hydrolysis of substrates with complex structures, which subsequently leads to low lactic acid (LA) production. Therefore, a novel strategy based on enzymatic pretreatment for improving LA production from anaerobic co-fermentation of SM and AW was proposed in this study. The results indicated that the maximal LA concentration increased from 35.89 ± 1.84 to 42.70 ± 2.18 g/L with the increase of enzyme loading from 0 to 300 U/g VS substrate . Mechanism exploration indicated that enzymatic pretreatment significantly promoted the release and hydrolysis of insoluble organic matter from fermentation substrate, thus providing an abundance of reaction intermediates that were directly available for LA production. Additionally, bacteria analysis revealed that the high concentration of LA was associated with the prevalence of Lactobacillus. This study offered an environmental-friendly strategy for promoting SM and AW hydrolysis and provided a viable approach for recovering valuable products., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

High-value chemical production from natural lignocellulose transformation is a reliable waste utilization approach. A gene encoding cold-adapted carboxylesterase in Arthrobacter soli Em07 was identified. The gene was cloned and expressed in Escherichia coli to obtain a carboxylesterase enzyme with a molecular weight of 37.2 KDa. The activity of the enzyme was determined using α-naphthyl acetate as substrate. Results showed that the optimum enzyme activity of carboxylesterase was at 10 °C and pH 7.0. It was also found that the enzyme could degrade 20 mg enzymatic pretreated de-starched wheat bran (DSWB) to produce 235.8 μg of ferulic acid under the same conditions, which was 5.6 times more than the control. Compared to the chemical strategy, enzymatic pretreatment is advantageous because it is environmentally friendly, and the by-products can be easily treated. Therefore, this strategy provides an effective method for high-value utilization of biomass waste in agriculture and industry., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Delignification of steam-exploded birch wood (SEBW) was stimulated using a pretreatment method including Fenton reaction (FR) and fungi. SEBW was employed as a substrate to optimize the Fe(III) and Fe(II) dosage in FR. Maximum iron-binding to SEBW was obtained at pH 3.5. FR pretreatment increased biological methane yields from 257 mL/g vS in control to 383 and 352 mL/ g vS in samples with 0.5 mM Fe(II) and 1.0 mM Fe(III), respectively. Further enzymatic pretreatment using a commercial cellulase cocktail clearly improved methane production rate but only increased the final methane yields by 2-9 %. Finally, pretreatments with the fungi Pleurotus ostreatus (PO) and Lentinula edodes (LE), alone or in combination with FR, were carried out. SEBW pretreated with only LE and samples pretreated with PO and1 mM Fe(III) + H 2 O 2 increased the methane production yield to 420 and 419 mL/g vS respectively. These pretreatments delignified SEBW up to 25 %., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Seyedbehnam Hashemi reports financial support, administrative support, article publishing charges, equipment, drugs, or supplies, travel, and writing assistance were provided by Norwegian University of Science and Technology. Svein Jarle Horn reports financial support and writing assistance were provided by Norwegian University of Life Sciences. Jacob J. Lamb reports statistical analysis and writing assistance were provided by Norwegian University of Science and Technology. Kristian M. Lien reports administrative support, equipment, drugs, or supplies, and writing assistance were provided by Norwegian University of Science and Technology. Seyedbehnam Hashemi reports a relationship with ENERSENSE strategic research program initiative that includes: funding grants and travel reimbursement. One of the co-authors works at the Norwegian institute for bioeconomy research (NIBIO)., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

This study introduced the excellent improvement of enzyme cocktail (lysozyme and protease) on hydrolysis efficiency and the role of reducing carbon emission as an alternative carbon source. The best dosing method after optimization was to add four parts of lysozyme at 0 h and one part of protease at 1 h. The extracellular proteins and polysaccharides increased by 118% and 64% respectively under the optimal dosing mode. Enzyme cocktails reduced more organic matters and extended the distribution of sludge particles in the small particle size part. The enzymatic-treated sludge could reduce 21.09 kg CO 2 /t VSS if utilized to replace methanol for denitrification carbon source. Enzyme cocktails did better in enhancing both solubilization and hydrolysis than single enzymes under the optimal method. This study will provide a more integrated and comprehensive system for enzymatic pretreatment and new insight into the enzymatic pretreatment enhancing hydrolysis and reducing carbon emission., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The main purpose of this study was to explore the pretreatment process of corn starch wastewater (CSW) and engineered microalgae cultivation strategy to improve the nutrient recovery from wastewater and the yield of microalgae lutein. One-stage enzymatic hydrolysis utilizing α-amylase and glucoamylase simultaneously was established to efficiently harvest a maximum concentration of reducing sugar content of 7.26 g/L from CSW in 50 min. Lutein yield of 10.96 mg/L was obtained under 24 h continuous illumination with 2200 Lux light intensity. Furthermore, a cyclic feeding cultivation strategy was developed to improve lutein accumulation and COD removal up to 25.9 mg/L and 50.7%, respectively, after three cultivation cycles. Lutein yield of 14.86 mg/L and COD removal efficiency of 73.2% was achieved with further implementation in actual wastewater. This work provided a new perspective in developing the potential of cultivating microalgae with corn starch wastewater to produce high-value lutein., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The high content of solid organics in food waste (FW) results in a low and unstable anaerobic digestion (AD) efficiency. Improving methane production rate and process stability is attracting much attention towards advanced AD of FW. The feasibility of advanced AD of FW pretreated with enzyme was investigated by batch experiments and 164 days running of an expanded granular sludge bed (EGSB) reactor. Simulation study based on the results of batch experiments indicates it is possible to treat enzymatically pretreated FW using an EGSB reactor. During the running of an EGSB reactor, the organic loading rate went up to 20 g chemical oxygen demand (COD)/L.d, and the total COD removal rate reached 88%. The significance of this study is to achieve an advanced AD of enzymatically pretreated FW with a stable and efficient methane production with biogas residue being reduced greatly., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Biological pretreatment is a promising technology to increase biogas yield. The methane yield and microbial community resulting from anaerobic digestion of maize straw after pretreatment of enzymes [extracted from Trichoderma viride (ETv) and Aspergillus sp. (EAs)] at different mixing ratios [5/0, 4/1, 3/2, 2/3, 1/4, 0/5] were evaluated. The methane yields from mixed enzymes pretreatment were higher than single enzymes pretreatments of ETv and EAs. The optimal enzymes mixing ratio of ETv and EAs was found to be 2/3, with the cumulative methane yield 512.64 mL/g TS added , which was 31.74% higher than the control. Enzymatic pretreatment promoted an increase in the abundance of bacteria and archaea associated with cellulose decomposition. The majority of bacteria and archaea were assigned to Bacteroidetes, Firmicutes and Methanosaeta., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

In this work, lignocellulosic nanofibrils (LCNF) produced from mechanical fibrillation with mixed enzymatic pretreatment or post-treatment were compared and the chemical composition, water retention value (WRV), average-number height and crystallinity for the obtained LCNF were evaluated. Compared to pure mechanical fibrillation, both mixed enzymatic pretreatment and post-treatment could efficiently facilitate cellulose nanofibrillation. Moreover, mixed enzymatic pretreatment was more suitable for LCNF production, resulting in a relatively higher WRV of 909% and smaller average-number height of 15 nm. These discoveries provide new insights into a more efficient biological method for the production and application of cellulose nanomaterials., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Enzymatic pretreatment has shown great potential in making the disintegration of cellulosic fibers to fibrils cost-effectively and environmental-friendly. In this study, an extensive commercial endoglucanase was used to pretreat cellulosic fibers for fibrillation. The pretreatment time and the enzyme dosage were optimized using response surface methodology. A 100% fiber recovery was obtained at endoglucanase usage of 9.0 mg/g (substrate) and pretreatment time of less than 3.0 h. A highly fibrillated and fractured surface of pretreated fibers was observed after 0.5 h of pretreatment compared to native fibers. Meanwhile, the progressive deconstruction of cellulosic fibers was occurred with the enzymatic pretreatment time increasing. The degree of deconstruction of fibers was evidenced by changes of the fiber microstructure, such as the inter-/intra-molecular H-bonds, the β-1,4-glucosidic linkages, crystallinity and crystallite size. These discoveries provide new insights into a more efficient and economic pretreatment methods for the disintegration of fibrils from cellulosic fibers., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

In order to improve the methane yield, the alkaline and biological pretreatments on anaerobic digestion (AD) were investigated. Three treatments were tested: NaOH, biological (enzyme and fungi), and combined NaOH with biological. The maximum reducing sugar concentrations were obtained using Enzyme T (2.20 mg/mL) on the 6th day. The methane yield of NaOH + Enzyme A was 300.85 mL/g TS, 20.24% higher than the control. Methane yield obtained from Enzyme (T + A) and Enzyme T pretreatments were 277.03 and 273.75 mL/g TS, respectively, which were as effective as 1% NaOH (276.16 mL/g TS) in boosting methane production, and are environmentally friendly and inexpensive biological substitutes. Fungal pretreatment inhibited methane fermentation of maize straw, 15.68% was reduced by T + A compared with the control. The simultaneous reduction of DM, cellulose and hemicellulose achieved high methane yields. This study provides important guidance for the application of enzymes to AD from lignocellulosic agricultural waste., (Copyright © 2017. Published by Elsevier Ltd.)

Although biological pretreatment of cellulosic fiber based on endoglucanases has shown some promise to facilitate cellulose nanofibrillation, its efficacy is still limited. In this study, a xylanase-aided endoglucanase pretreatment was assessed on the bleached hardwood and softwood Kraft pulps to facilitate the downstream cellulose nanofibrillation. Four commercial xylanase preparations were compared and the changes of major fiber physicochemical characteristics such as cellulose/hemicellulose content, gross fiber properties, fiber morphologies, cellulose accessibility/degree of polymerization (DP)/crystallinity were systematically evaluated before and after enzymatic pretreatment. It showed that the synergistic cooperation between endoglucanase and certain xylanase (Biobrite) could efficiently "open up" the hardwood Kraft pulp with limited carbohydrates degradation (<7%), which greatly facilitated the downstream cellulose nanofibrillation during mild sonication process (90Wh) with more uniform disintegrated nanofibril products (50-150nm, as assessed by scanning electron microscopy and UV-vis spectroscopy)., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Marine macroalgae are gaining more and more importance as a renewable feedstock for durable bioenergy production, but polysaccharides of this macroalgae are structurally complex in its chemical composition. The use of enzymatic hydrolysis may provide new pathways in the conversion of complex polysaccharides to fermentable sugars. In this study, an enzymatic cocktail with high specificity was first isolated from Aspergillus niger using the green macroalgae Ulva rigida as nitrogen source. The cocktail is rich on β-glucosidase, pectinase and carboxy-methyl-cellulase (CMCase). The highest activity was obtained with β-glucosidase (109IUmL(-1)) and pectinase (76IUmL(-1)), while CMCase present the lowest activity 4.6IUmL(-1). The U. rigida pre-treatment with this enzymatic cocktail showed high rate of reduced sugar release, and could bring promising prospects for enzymatic pre-treatment of the biogas production from U. rigida biomass which reached 1175mLgCODint(-1)., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Pretreatment of lignocellulosic biomass is necessary to enhance the hydrolysis, which is the rate-limiting step in biogas production. Laccase and versatile peroxidase are enzymes known to degrade lignin. Therefore, the impact of enzymatic pretreatment was studied on a variety of biomass. A significant higher release in total phenolic compounds (TPC) was observed, never reaching the inhibiting values for anaerobic digestion. The initial concentration of TPC was higher in the substrates containing more lignin, miscanthus and willow. The anaerobic digestion of these two substrates resulted in a significant lower biomethane production (68.8-141.7 Nl/kg VS). Other substrates, corn stover, flax, wheat straw and hemp reached higher biomethane potential values (BMP), between 241 and 288 Nl/kg VS. Ensilaged maize reached 449 Nl/kg VS, due to the ensilation process, which can be seen as a biological and acid pretreatment. A significant relation (R(2) = 0.89) was found between lignin content and BMP., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In this study, a fungal mash rich in hydrolytic enzymes was produced by solid state fermentation (SSF) of waste cake in a simple and efficient manner and was further applied for high-efficiency hydrolysis of mixed food wastes (FW). The enzymatic pretreatment of FW with this fungal mash resulted in 89.1 g/L glucose, 2.4 g/L free amino nitrogen, 165 g/L soluble chemical oxygen demand (SCOD) and 64% reduction in volatile solids within 24h. The biomethane yield and production rate from FW pretreated with the fungal mash were found to be respectively about 2.3 and 3.5-times higher than without pretreatment. After anaerobic digestion of pretreated FW, a volatile solids removal of 80.4±3.5% was achieved. The pretreatment of mixed FW with the fungal mash produced in this study is a promising option for enhancing anaerobic digestion of FW in terms of energy recovery and volume reduction., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Results of sugar beet pulp silage (SBPS) and vinasse (mixed in weight ratios of 3:1, 1:1 and 1:3, respectively) co-fermentation, obtained in this study, provide evidence that addition of too high amount of vinasse into the SBPS decreases biogas yields. The highest biogas productivity (598.1mL/g VS) was achieved at the SBPS-vinasse ratio of 3:1 (w/w). Biogas yields from separately fermented SBPS and vinasse were by 13% and 28.6% lower, respectively. It was found that enzymatic pretreatment of SBPS before methane fermentation that caused partial degradation of component polysaccharides, considerably increased biogas production. The highest biogas yield (765.5mL/g VS) was obtained from enzymatic digests of SBPS-vinasse (3:1) blend (27.9% more than from fermentation of the counterpart blend, which was not treated with enzymes). The simulation of potential biogas production from all the aforementioned mixtures using the Gompertz equation showed fair fit to the experimental results., (Copyright © 2014 Elsevier Ltd. All rights reserved.)