Enzymatic hydrolysis of brewer's spent grain to obtain fermentable sugars

Successive process for efficient biovalorization of Brewers' spent grain to lignocellulolytic enzymes and lactic acid production through simultaneous saccharification and fermentation

This study aimed to increase the value of brewers' spent grain (BSG) by using it as feedstock to produce lignocellulolytic enzymes and lactic acid (LA). Twenty-two fungal strains were screened for lignocellulolytic enzyme production from BSG. Among them, Trichoderma sp. showed the highest cellulase activity (35.84 ± 0.27 U/g-BSG) and considerably high activities of xylanase (599.61 ± 23.09 U/g-BSG) and β-glucosidase (16.97 ± 0.77 U/g-BSG) under successive solid-state and submerged fermentation. The processes were successfully scaled up in a bioreactor. The enzyme cocktail was recovered and characterized. The maximum cellulase and xylanase activities were found at pH 5.0 and 50 °C, and the activities were highly stable at pH 4-8 and 30-50 °C. The enzyme cocktail was applied in simultaneous saccharification and fermentation of acid-pretreated BSG for LA production. The maximum LA obtained was 59.3 ± 1.0 g/L. This study has shown the efficient biovalorization of BSG, and this approach may also be applicable to other agro-industrial wastes.

Production of single cell protein from brewer's spent grain through enzymatic saccharification and fermentation enhanced by ammoniation pretreatment

Brewer's spent grain (BSG) is a major low-value by-product of beer industry. To realize the high value application of BSG, this work proposed a strategy to produce single cell protein (SCP) with oligosaccharide prebiotics from BSG, via ammoniation pretreatment, enzymatic hydrolysis, and fermentation. The optimum conditions of ammoniation pretreatment obtained by response surface method were 11 % ammonia dosage (w/w), 63 °C for 26 h. Suitable enzyme and yeast were screened to enhance the conversion of cellulose and hemicellulose in BSG into sugars and maximize the SCP yield. It was shown that using lignocellulolytic enzyme SP from Penicillium oxalicum and Trichosporon cutaneum, about 310 g of SCP with 80 g of arabinoxylo-oligosaccharides were obtained from 1000 g of BSG. This process is low cost, high efficiency, and easy to implement, which has good industrial application prospects.

Microbial alchemy: upcycling of brewery spent grains into high-value products through fermentation

Spent grains are one of the lignocellulosic biomasses available in abundance, discarded by breweries as waste. The brewing process generates around 25-30% of waste in different forms and spent grains alone account for 80-85% of that waste, resulting in a significant global waste volume. Despite containing essential nutrients, i.e., carbohydrates, fibers, proteins, fatty acids, lipids, minerals, and vitamins, efficient and economically viable valorization of these grains is lacking. Microbial fermentation enables the valorization of spent grain biomass into numerous commercially valuable products used in energy, food, healthcare, and biomaterials. However, the process still needs more investigation to overcome challenges, such as transportation, cost-effective pretreatment, and fermentation strategy. to lower the product cost and to achieve market feasibility and customer affordability. This review summarizes the potential of spent grains valorization via microbial fermentation and associated challenges.

Protein recovery from brewery solid wastes

Brewing produces significant amounts of solid waste during the process: spent cereals (BSG), hops and spent yeast (BSY). These residues are sustainable sources of valuable nutrients and functional compounds like proteins, polyphenols, and polysaccharides. This review describes the three solid wastes and the different extraction techniques for protein recovery. The protein obtained can be used as a new source of non-animal protein or as a functional and bioactive ingredient. Particular attention was given to methods using conventional technologies (alkaline and ethanolic extraction) and more innovative approaches (enzymes, microwaves, ultrasound, pressurized liquids and sub-critical water extraction). Although the BSG is used in some industrial applications, studies in operating conditions, cost, energy efficiency, and product performance are still required to consolidate these solid wastes as a source of non-animal protein. The application of proteins is also an important question when choosing the extraction method.

Treatment of distiller grain with wet-process phosphoric acid leads to biochar for the sustained release of nutrients and adsorption of Cr(VI)

Soil amendment products, such as biochar, with both sustained nutrient release and heavy metal retention properties are of great need in agricultural and environmental industries. Herein, we successfully prepared a new biochar material with multinutrient sustained-release characteristics and chromium removal potential derived from distiller grain by wet-process phosphoric acid (WPPA) modification without washing. SEM, TEM TG-IR, in situ DRIFTS and XRD characterization indicated that biochar and polyphosphate formed simultaneously and were tightly intertwined by one-step pyrolysis. The optimal product (PKBC-400) had the most stable carbon structure and an adequate P-O-P structure with less P loss. Batch experiments illustrated that 92.83% P (ortho-P), 85.94% K, 41.49% Fe, 78.42% Al and 65.60% Mg were continuously released in water from PKBC-400 within 63 days, and the maximum Cr removal rate reached 83.57% (50 mg/L K₂Cr₂O₇, pH=3.0) with an increased BET surface area (304.0557 m²/g) after nutrient release. SEM, IC and ³¹P NMR analyses revealed that the dissolution and hydrolysis of polyphosphates not only realized the sustained release of multiple nutrients but also significantly improved the sustained release performance. The proposed resource utilization strategy provided new ideas for Cr hazard control, biomass waste utilization and fertilizer development.

Biorefinery of Brewery Spent Grain by Solid-State Fermentation and Ionic Liquids

Novel environmentally friendly pretreatments have been developed in recent years to improve biomass fractionation. Solid-state fermentation (SSF) and treatment with ionic liquids show low environmental impact and can be used in biorefinery of biomass. In this work, these processes were assessed with brewery spent grain (BSG). First, BSG was used as a substrate to produce cellulases and xylanases by SSF with the fungi Aspergillus brasiliensis CECT 2700 and Trichoderma reesei CECT 2414. Then, BSG was pretreated with the ionic liquid [N₁₁₁₂OH][Gly] and hydrolyzed with the crude enzymatic extracts. Results showed that SSF of BSG with A. brasiliensis achieved the highest enzyme production; meanwhile, the pretreatment with ionic liquids allowed glucan and xylan fractions to increase and reduce the lignin content. In addition, a mixture of the extracts from both fungi in a ratio of 2.5:0.5 Aspergillus/Trichoderma (v/v) efficiently hydrolyzed the BSG previously treated with the ionic liquid [N₁₁₁₂OH][Gly], reaching saccharification percentages of 80.68%, 54.29%, and 19.58% for glucan, xylan, and arabinan, respectively. In conclusion, the results demonstrated that the BSG biorefinery process developed in this work is an effective way to obtain fermentable sugar-containing solutions, which can be used to produce value-added products.

Grain bran hydrolysates in the production of fruit distillates

Currently, there is an urgent need for domestic fermentation activators based on low-cost secondary raw materials. We aimed to study the effect of microbial enzyme preparations with different action on the hydrolysis of proteins and phytin of grain bran to obtain fermentation activators that could become an alternative to imported ones. We studied wheat and rye brans; microbial enzyme preparations with cytolytic, proteolytic, and phytase action; multi-enzyme compositions; and grain bran hydrolysates. Firstly, we determined the kinetic characteristics of enzyme preparations. Secondly, we evaluated their effectiveness in the hydrolysis of the brans. Thirdly, we developed multi-enzyme compositions. Finally, we determined the concentration of soluble forms of phosphorus and free amino acids in the hydrolysates. We determined optimal temperature and pH values for the enzyme preparations. The multi-enzyme compositions contributed to a high accumulation of reducing substances, water-soluble protein, and phosphorus. The concentration of free amino acids in the hydrolysates obtained under the action of the bran’s own enzymes was about 20% higher in the wheat samples, compared to the rye samples. However, when using multi-enzyme compositions in addition to the bran’s own enzymes, the concentration of free amino acids was 1.5 times higher in the rye hydrolysates, compared to the wheat hydrolysates. The use of multi-enzyme compositions under optimal conditions can double the content of phosphorus and free amino acids available for yeast, compared to the control. Our results can be used for further research into using grain bran hydrolysates as an alternative source of nitrogen and phosphorus nutrition for yeast at the fermentation stage of fruit distillate production.

Valorization of Brewer’s Spent Grain Using Biological Treatments and its Application in Feeds for European Seabass (Dicentrarchus labrax)

Brewer’s spent grain (BSG) is the main brewery industry by-product, with potential applications in the feed and food industries due to its carbohydrate composition. In addition, the lignocellulosic nature of BSG makes it an adequate substrate for carbohydrases production. In this work, solid-state fermentation (SSF) of BSG was performed with Aspergillus ibericus, a non-mycotoxin producer fungus with a high capacity to hydrolyze the lignocellulosic matrix of the agro-industrial by-products. SSF was performed at different scales to produce a crude extract rich in cellulase and xylanase. The potential of the crude extract was tested in two different applications: -(1) - the enzymatic hydrolysis of the fermented BSG and (2) - as a supplement in aquafeeds. SSF of BSG increased the protein content from 25% to 29% (w/w), while the fiber content was reduced to 43%, and cellulose and hemicellulose contents were markedly reduced to around 15%. The scale-up of SSF from 10 g of dry BSG in flasks to 50 g or 400 g in tray-type bioreactors increased 55% and 25% production of cellulase and xylanase, up to 323 and 1073 U g⁻¹ BSG, respectively. The optimum temperature and pH of maximal activities were found to be 55°C and pH 4.4 for xylanase and 50°C and pH 3.9 for cellulase, cellulase being more thermostable than xylanase when exposed at temperatures from 45°C to 60°C. A Box–Behnken factorial design was applied to optimize the hydrolysis of the fermented BSG by crude extract. The crude extract load was a significant factor in sugars release, highlighting the role of hydrolytic enzymes, while the load of fermented BSG, and addition of a commercial β-glucosidase were responsible for the highest phenolic compounds and antioxidant activity release. The lyophilized crude extract (12,400 and 1050 U g⁻¹ lyophilized extract of xylanase and cellulase, respectively) was also tested as an enzyme supplement in aquafeed for European seabass (Dicentrarchus labrax) juveniles. The dietary supplementation with the crude extract significantly improved feed and protein utilization. The processing of BSG using biological treatments, such as SSF with A. ibericus, led to the production of a nutritionally enriched BSG and a crude extract with highly efficient carbohydrases capable of hydrolyzing lignocellulosic substrates, such as BSG, and with the potential to be used as feed enzymes with remarkable results in improving feed utilization of an important aquaculture fish species.

Production of Different Biochemicals by Paenibacillus polymyxa DSM 742 From Pretreated Brewers' Spent Grains

Brewers' spent grains (BSG) are a by-product of the brewing industry that is mainly used as feedstock; otherwise, it has to be disposed according to regulations. Due to the high content of glucose and xylose, after pretreatment and hydrolysis, it can be used as a main carbohydrate source for cultivation of microorganisms for production of biofuels or biochemicals like 2,3-butanediol or lactate. 2,3-Butanediol has applications in the pharmaceutical or chemical industry as a precursor for varnishes and paints or in the food industry as an aroma compound. So far, Klebsiella pneumoniae, Serratia marcescens, Clostridium sp., and Enterobacter aerogenes are being used and investigated in different bioprocesses aimed at the production of 2,3-butanediol. The main drawback is bacterial pathogenicity which complicates all production steps in laboratory, pilot, and industrial scales. In our study, a gram-positive GRAS bacterium Paenibacillus polymyxa DSM 742 was used for the production of 2,3-butanediol. Since this strain is very poorly described in literature, bacterium cultivation was performed in media with different glucose and/or xylose concentration ranges. The highest 2,3-butanediol concentration of 18.61 g l-1 was achieved in medium with 70 g l-1 of glucose during 40 h of fermentation. In contrast, during bacterium cultivation in xylose containing medium there was no significant 2,3-butanediol production. In the next stage, BSG hydrolysates were used for bacterial cultivation. P. polymyxa DSM 742 cultivated in the liquid phase of pretreated BSG produced very low 2,3-butanediol and ethanol concentrations. Therefore, this BSG hydrolysate has to be detoxified in order to remove bacterial growth inhibitors. After detoxification, bacterium cultivation resulted in 30 g l-1 of lactate, while production of 2,3-butanediol was negligible. The solid phase of pretreated BSG was also used for bacterium cultivation after its hydrolysis by commercial enzymes. In these cultivations, P. polymyxa DSM 742 produced 9.8 g l-1 of 2,3-butanediol and 3.93 g l-1 of ethanol. On the basis of the obtained results, it can be concluded that different experimental setups give the possibility of directing the metabolism of P. polymyxa DSM 742 toward the production of either 2,3-butanediol and ethanol or lactate.

Enzymes-Assisted Extraction of Plants for Sustainable and Functional Applications

The scientific community and industrial companies have discovered significant enzyme applications to plant material. This rise imparts to changing consumers’ demands while searching for ‘clean label’ food products, boosting the immune system, uprising resistance to bacterial and fungal diseases, and climate change challenges. First, enzymes were used for enhancing production yield with mild and not hazardous applications. However, enzyme specificity, activity, plant origin and characteristics, ratio, and extraction conditions differ depending on the goal. As a result, researchers have gained interest in enzymes’ ability to cleave specific bonds of macroelements and release bioactive compounds by enhancing value and creating novel derivatives in plant extracts. The extract is enriched with reducing sugars, phenolic content, and peptides by disrupting lignocellulose and releasing compounds from the cell wall and cytosolic. Nonetheless, depolymerizing carbohydrates and using specific enzymes form and release various saccharides lengths. The latest studies show that oligosaccharides released and formed by enzymes have a high potential to be slowly digestible starches (SDS) and possibly be labeled as prebiotics. Additionally, they excel in new technological, organoleptic, and physicochemical properties. Released novel derivatives and phenolic compounds have a significant role in human and animal health and gut-microbiota interactions, affecting many metabolic pathways. The latest studies have contributed to enzyme-modified extracts and products used for functional, fermented products development and sustainable processes: in particular, nanocellulose, nanocrystals, nanoparticles green synthesis with drug delivery, wound healing, and antimicrobial properties. Even so, enzymes’ incorporation into processes has limitations and is regulated by national and international levels.

Solid-state fermented brewer's spent grain enzymatic extract increases in vitro and in vivo feed digestibility in European seabass

Brewer's spent grain (BSG) is the largest by-product originated from the brewery industry with a high potential for producing carbohydrases by solid-state fermentation. This work aimed to test the efficacy of a carbohydrases-rich extract produced from solid-state fermentation of BSG, to enhance the digestibility of a plant-based diet for European seabass (Dicentrarchus labrax). First, BSG was fermented with A. ibericus to obtain an aqueous lyophilized extract (SSF-BSG extract) and incorporated in a plant-based diet at increasing levels (0-control; 0.1%, 0.2%, and 0.4%). Another diet incorporating a commercial carbohydrases-complex (0.04%; Natugrain; BASF) was formulated. Then, all diets were tested in in vitro and in vivo digestibility assays. In vitro assays, simulating stomach and intestine digestion in European seabass, assessed dietary phosphorus, phytate phosphorus, carbohydrates, and protein hydrolysis, as well as interactive effects between fish enzymes and dietary SSF-BSG extract. After, an in vivo assay was carried out with European seabass juveniles fed selected diets (0-control; 0.1%, and 0.4%). In vitro digestibility assays showed that pentoses release increased 45% with 0.4% SSF-BSG extract and 25% with Natugrain supplemented diets, while amino acids release was not affected. A negative interaction between endogenous fish enzymes and SSF-BSG extract was observed in both diets. The in vivo digestibility assay corroborated in vitro data. Accordingly, the dietary supplementation with 0.4% SSF-BSG increased the digestibility of dry matter, starch, cellulose, glucans, and energy and did not affect protein digestibility. The present work showed the high potential of BSG to produce an added-value functional supplement with high carbohydrases activity and its potential contribution to the circular economy by improving the nutritional value of low-cost and sustainable ingredients that can be included in aquafeeds.

Brewers' spent grain as carbon source for itaconate production with engineered Ustilago maydis

Brewers' spent grain (BSG) is produced worldwide in millions of tons during the beer brewing process. Due to its high content of structural carbohydrates, BSG is a promising material for being valorised in biorefineries. In this study three process routes for producing itaconate from BSG hydrolysates are presented using the previously engineered smut fungi UstilagomaydisMB215Δcyp3ΔP_ria1::P_etef as whole-cell biocatalyst. Using a fermentation medium based on BSG hydrolysate a yield of 0.38g_Ita/g_Sugar and a productivity of 0.11g_Ita/(L·h) were achieved. The addition of detoxified hydrothermal supernatant to the fermentation medium did not result in improved performance parameters but resulted in a decreased yield (0.29g_Ita/g_Sugar) and productivity (0.053 g_Ita/(L·h)). Simultaneous saccharification and fermentation with hydrothermal pretreated BSG is possible, although at lower rate. In summary, the valorisation of BSG in fungal fermentations might complement the end-of-life options of this industrial side product.

Optimised Fractionation of Brewer’s Spent Grain for a Biorefinery Producing Sugars, Oligosaccharides, and Bioethanol

Brewer’s spent grain (BSG) is the main by-product of the beer brewing process. It has a huge potential as a feedstock for bio-based manufacturing processes to produce high-value bio-products, biofuels, and platform chemicals. For the valorisation of BSG in a biorefinery process, efficient fractionation and bio-conversion processes are required. The aim of our study was to develop a novel fractionation of BSG for the production of arabinose, arabino-xylooligomers, xylose, and bioethanol. A fractionation process including two-step acidic and enzymatic hydrolysis steps was investigated and optimised by a response surface methodology and a desirability function approach to fractionate the carbohydrate content of BSG. In the first acidic hydrolysis, high arabinose yield (76%) was achieved under the optimised conditions (90 °C, 1.85 w/w% sulphuric acid, 19.5 min) and an arabinose- and arabino-xylooligomer-rich supernatant was obtained. In the second acidic hydrolysis, the remaining xylan was solubilised (90% xylose yield) resulting in a xylose-rich hydrolysate. The last, enzymatic hydrolysis step resulted in a glucose-rich supernatant (46 g/L) under optimised conditions (15 w/w% solids loading, 0.04 g/g enzyme dosage). The glucose-rich fraction was successfully used for bioethanol production (72% ethanol yield by commercial baker’s yeast). The developed and optimised process offers an efficient way for the value-added utilisation of BSG. Based on the validated models, the amounts of the produced sugars, the composition of the sugar streams and solubilised oligo-saccharides are predictable and variable by changing the reaction conditions of the process.

Brewer's spent grain as a no-cost substrate for polyhydroxyalkanoates production: Assessment of pretreatment strategies and different bacterial strains

Polyhydroxyalkanoates (PHAs) are polyesters of significant interest due to their biodegradability and properties similar to petroleum-derived plastics, as well as the fact that they can be produced from renewable sources such as by-product streams. In this study, brewer's spent grain (BSG), the main by-product of the brewing industry, was subjected to a set of physicochemical pretreatments and their effect on the release of reducing sugars (RS) was evaluated. The RS obtained were used as a substrate for further PHA production in Burkholderia cepacia, Bacillus cereus, and Cupriavidus necator in liquid cultures. Although some pretreatments proved efficient in releasing RS (acid-thermal pretreatment up to 42.1 gRS L^-1 and 0.77 gRS g^-1 dried BSG), the generation of inhibitors in such scenarios likely affected PHA production compared with the process run without pretreatment (direct enzymatic hydrolysis of BSG). Thus, the maximum PHA accumulation from BSG hydrolysates was found in the reference case with 0.31 ± 0.02 g PHA per g cell dried weight, corresponding to 1.13 ± 0.06 g L^-1 and a PHA yield of 23 ± 1 mg g^-1 BSG. It was also found that C. necator presented the highest PHA accumulation of the tested strains followed closely by B. cepacia, reaching their maxima at 48 h. Although BSG has been used as a source for other bioproducts, these results show the potential of this by-product as a no-cost raw material for producing PHAs in a waste valorization and circular economy scheme.

Valorization of Vegetable Food Waste and By-Products Through Fermentation Processes

There is a general interest in finding new ways of valorizing fruit and vegetable processing by-products. With this aim, applications of industrial fermentation to improve nutritional value, or to produce biologically active compounds, have been developed. In this sense, the fermentation of a wide variety of by-products including rice, barley, soya, citrus, and milling by-products has been reported. This minireview gives an overview of recent fermentation-based valorization strategies developed in the last 2 years. To aid the designing of new bioprocesses of industrial interest, this minireview also provides a detailed comparison of the fermentation conditions needed to produce specific bioactive compounds through a simple artificial neural network model. Different applications reported have been focused on increasing the nutritional value of vegetable by-products, while several lactic acid bacteria and Penicillium species have been used to produce high purity lactic acid. Bacteria and fungi like Bacillus subtilis, Rhizopus oligosporus, or Fusarium flocciferum may be used to efficiently produce protein extracts with high biological value and a wide variety of functional carbohydrates and glycosidases have been produced employing Aspergillus, Yarrowia, and Trichoderma species. Fermentative patterns summarized may guide the production of functional ingredients for novel food formulation and the development of low-cost bioprocesses leading to a transition toward a bioeconomy model.

The role of microorganisms on biotransformation of brewers' spent grain

Brewers' spent grain (BSG) is the most abundant by-product of brewing. Due to its microbiological instability and high perishability, fresh BSG is currently disposed of as low-cost cattle feed. However, BSG is an appealing source of nutrients to obtain products with high added value through microbial-based transformation. As such, BSG could become a potential source of income for the brewery itself. While recent studies have covered the relevance of BSG chemical composition in detail, this review aims to underline the importance of microorganisms from the stabilization/contamination of fresh BSG to its biotechnological exploitation. Indeed, the evaluation of BSG-associated microorganisms, which include yeast, fungi, and bacteria, can allow their safe use and the best methods for their exploitation. This bibliographical examination is particularly focused on the role of microorganisms in BSG exploitation to (1) produce enzymes and metabolites of industrial interest, (2) supplement human and animal diets, and (3) improve soil fertility. Emerging safety issues in the use of BSG as a food and feed additive is also considered, particularly considering the presence of mycotoxins.Key points• Microorganisms are used to enhance brewers' spent grain nutritional value.• Knowledge of brewers' spent grain microbiota allows the reduction of health risks. Graphical abstract.

Chemoenzymatic conversion of Sorghum durra stalk into furoic acid by a sequential microwave-assisted solid acid conversion and immobilized whole-cells biocatalysis

In this study, chemoenzymatic conversion of Sorghum durra stalk (SDS) into furoic acid was developed by a sequential microwave-assisted solid acid conversion and immobilized whole-cells biocatalysis method. Dry dewaxed SDS (75 g/L) was catalyzed into furfural at 57.8% yield with heterogeneous Sn-argil (2.0 wt% dosage) in n-ethyl butyrate-H₂O (1:1, v:v) biphasic system using a microwave (600 W) for 10 min at 180 °C. In this biphasic media (pH 6.5), SDS-derived furfural (125.0 mM) was biologically oxidized to furoic acid by immobilized Brevibacterium lutescens cells harboring furfural-oxidizing activity at 30 °C, and furfural was wholly transformed to furoic acid within 24 h. Finally, the recovery and reuse of the Sn-argil catalyst and immobilized biocatalysts were conducted for synthesizing furoic acid from SDS in the biphasic system. This chemoenzymatic route can be attractive for furoic acid production.

Water Ultrasound-Assisted Extraction of Polyphenol Compounds from Brewer's Spent Grain: Kinetic Study, Extract Characterization, and Concentration

Brewer's spent grain (BSG) was chemically characterized obtaining 52.1% of carbohydrates, 17.8% protein, 5.9% lipids, 13.5% insoluble lignin and 24.3% of water-soluble extractives. This work has been focused on the study of polyphenol extraction of the extractive fraction by water ultrasound-assisted extraction. Selected extraction conditions were 47 °C and 21.7 mL water/g_dry-BSG. The effect of solvent polarity on polyphenol extraction was studied by using ethanol aqueous mixtures, from 20% to 100% ethanol. The kinetics of polyphenol extraction have been fitted to the power law and the Weibull models yielding mean values of the root mean square deviation lower than 7.5%. Extracts have been characterized in terms of quantification of individual phenolic compounds by HPLC-DAD and protein and sugar soluble fractions (glucose, xylose, and arabinose). Polyphenol profile has been compared with other hydrolytic techniques, such as acid, basic and enzymatic hydrolysis, showing that ultrasound was not as effective as basic hydrolysis to release the phenolic acids esterified to the cell wall. A further centrifuge ultrafiltration concentration step was able to yield a retentate enriched in the protein fraction while individual phenolic compounds where mainly transferred to the permeate.

Low-Cost Cellulase-Hemicellulase Mixture Secreted by Trichoderma harzianum EM0925 with Complete Saccharification Efficacy of Lignocellulose

Fermentable sugars are important intermediate products in the conversion of lignocellulosic biomass to biofuels and other value-added bio-products. The main bottlenecks limiting the production of fermentable sugars from lignocellulosic biomass are the high cost and the low saccharification efficiency of degradation enzymes. Herein, we report the secretome of Trichoderma harzianum EM0925 under induction of lignocellulose. Numerously and quantitatively balanced cellulases and hemicellulases, especially high levels of glycosidases, could be secreted by T. harzianum EM0925. Compared with the commercial enzyme preparations, the T. harzianum EM0925 enzyme cocktail presented significantly higher lignocellulolytic enzyme activities and hydrolysis efficiency against lignocellulosic biomass. Moreover, 100% yields of glucose and xylose were obtained simultaneously from ultrafine grinding and alkali pretreated corn stover. These findings demonstrate a natural cellulases and hemicellulases mixture for complete conversion of biomass polysaccharide, suggesting T. harzianum EM0925 enzymes have great potential for industrial applications.

Structural and Physicochemical Characteristics of Rice Bran Dietary Fiber by Cellulase and High-Pressure Homogenization

The present paper aims to study the effect of cellulase hydrolysis and high-pressure homogenization on the structural and physicochemical properties of rice bran dietary fiber (RB-DF). Scanning electron microscopy showed that cellulase treatment led to the formation of a porous structure on RB-DF surface. High-pressure homogenization affected the laminated microstructure of RB-DF, leading to the formation of an irregular and loose surface structure. X-ray diffraction demonstrated that joint processing destroyed the amorphous hemicellulose and cellulose regions, and changed the crystallinity of RB-DF, albeit with a minor impact on the crystalline region of cellulose. Fourier transform infrared spectroscopy indicated that combined processing promoted dissociation of some glycosidic bonds in fiber structure, exposing the hydroxyl groups in cellulose, thus improving their ability to bind water molecules. Thermogravimetric analysis showed a significant decrease in the thermal decomposition temperature of RB-DF (p <0.05) as well as a decrease in thermal stability after combined processing. Cellulase hydrolysis and high-pressure homogenization treatment did not improve their oil holding capacity, but significantly increased water holding capacity, swelling capability, and cation exchange capacity of RB-DF. Thus, enzymatic hydrolysis and high-pressure homogenization treatment can change the structure of RB-DF, exposing a large number of hydrophilic groups and enhancing hydration, obtaining uniform RB-DF particle.