Solid-state Fermentation Conditions Research Articles

Comparative Analysis of Ligninolytic Potential among Pleurotus ostreatus and Fusarium sp. with a Special Focus on Versatile Peroxidase

Lignocellulosic biomass is contemplated to be an inexpensive and copious feedstock that can be used for numerous industrial applications. However, lignin forms the lignin sheath and provides a physical barrier to enzymatic hydrolysis. In addition, lignin physically blocks cellulase, preventing it from being combined with the substrate in a process known as non-productive binding. Therefore, the depletion of lignin is a crucial method for obtaining fermentable sugars from the lignocellulosic biomass. Different white-rot fungi secrete different sets of lignin-mineralizing enzymes and each fungus secretes one or more of the three enzymes essential for lignin degradation. Among efficient redox enzymes, versatile peroxidase is extensively studied for its ability to degrade aromatics without the need for a mediator or polyvalent catalytic site. However, the presence of versatile peroxidase in F. spp. has not been studied. This study was planned with the objective of screening and comparing the production of versatile peroxidase enzymes from F. spp. and a standard culture of Pleurotus ostreatus MTCC-142. These fungal strains were first screened on solid media containing tannic acid, malachite green, or bromocresol green. The potency index for the tannic acid, malachite green, and bromocresol green on the 16th day of incubation was reported to be 1.28, 1.07, 1.09, and 1.10, respectively. Versatile peroxidase production patterns were investigated under solid state fermentation conditions for a period of 25 days at different temperatures ranging from 10 to 35 °C. The highest versatile peroxidase activity (592 UL−1) in F. sp. was observed at 30 °C after the 7th day of incubation. The molecular confirmation showed the presence of the vp gene in F. sp. along with Pleurotus ostreatus MTCC-142. The results determined that F. sp. possesses a versatile peroxidase enzyme and is able to degrade lignin efficiently, and thus it could be utilized as an alternative to other ligninolytic enzyme-producing fungi.

Production and characterization of acidophilic xylanase from wood degrading white rot fungus by solid-state fermentation of wheat straw

Xylanases (EC 3.2.1.8) catalyze the breakdown of xylan, which is the second most abundant polysaccharide in plant cell walls. Biological catalysts have gained greater global attention than chemical catalysts in different industrial processes because they are highly selective, easy to control and have a negligible environmental impact. The aim of this study was to investigate the xylanolytic potential of white-rot fungi, optimize their physicochemical conditions and characterize the resulting xylanase. Sixty-eight white-rot fungus (WRF) isolates were screened for their xylanolytic potential and growth conditions for maximal xylanase production using cheap agricultural residue (wheat straw) as the sole carbon source. Five WRF isolates with high xylanase yields (73.63 ± 0.0283–63.6 ± 0.01247 U/ml) were selected by qualitative and quantitative screening methods. The optimum xylanase production occurred at pH 5.0 and 28 °C. Solid-state fermentation (SSF) yielded a high amount of xylanase. The highest xylanase activity (80.9–61.274 U/mL) was recorded in the pH range of 5.0–6.5 and at 50 °C. The metal ions Mg2+, Ca2+ and Mn2+ enhanced the activity of xylanase (127.28–110.06 %), while Cu2+, Fe2+ and K+ inhibited the activity with 43.4–17 % losses. The km and Vmax were 0.32–0.545 mg/mL and 86.95–113.63 μmol/min/mg, respectively. This finding indicates that wheat straw can be used for large-scale xylanase production under SSF conditions. The pH and temperature profiles and stabilities indicate that the xylanase produced in the present study can be applied in food and animal feed industries.

Peptide production through enhanced solid-state fermentation of soybean meal with Bacillus subtilis SBM_1: Fermentation process and product characteristics

This study aimed to assess the impact of additional inoculation of Bacillus subtilis SBM_1 on solid-state fermentation (SSF) of soybean meal (SBM). The peptide yield of fermented SBM increased to 220.93 mg/g under the optimal SSF conditions, marking a 47.74 % rise compared to natural SSF. Throughout enhanced SSF, the physicochemical properties of metabolites were analyzed. The results showed that the pH and total bacterial counts increased in the initial 8 h, along with elevated levels of peptide, soluble protein, and free amino acid (FAA). Protease activities is maintained at a relatively high level (103.37–241.93 U/g), leading to the substantial degradation of trypsin inhibitor (TI) and macromolecular protein. Following enhanced SSF, the TI activity of the fermented SBM decreased by 76.11 %, and small peptides with molecular weight (MW) < 3000 Da dominated the fermented products (71.64 %). Additionally, the enhanced SSF process demonstrated an improvement in nutrient content in the fermented products. Structural analysis of the fermented SBM showed that macromolecular soybean globulin and allergenic proteins were degraded, with the unfolded and loosened protein spatial structures and the loosely packed and dispersed surface microstructure. Biosafety analysis revealed no detectable microbial contaminants, including mold, salmonella, and coliforms, in compliance with national standards.

Effects of Fungal Solid-State Fermentation on the Profile of Phenolic Compounds and on the Nutritional Properties of Grape Pomace.

Grape pomace (GP) is considered a natural source of bioactive compounds. To improve the extractability of bioactive compounds, in this work, GP was biologically treated for 15 days with the white-rot fungus Trametes versicolor in laboratory jars and a tray bioreactor under solid-state fermentation (SSF) conditions. During SSF, the activity of lignolytic (laccase and manganese peroxidase) and hydrolytic (xylanase, cellulase, β-glucosidase, and invertase) enzymes was measured, with the activities of laccase (2.66 U/gdb in jars and 0.96 U/gdb in the bioreactor) and xylanase (346.04 U/gdb in jars and 200.65 U/gdb in the bioreactor) being the highest. The effect of the complex enzyme system was reflected in the changes in the chemical composition of GP with increasing ash, crude protein, and free fat content: 28%, 10%, and 17% in the laboratory jars, and 29%, 11%, and 7% in the bioreactor, respectively. In addition, the biological treatment improved the extractability of 13 individual phenolic compounds. Therefore, the applied SSF technique represents an effective strategy to improve the profile of phenolic compounds and the nutritional composition of GP, promoting their valorization and opening the door for potential applications in the food industry and other sectors.

Evaluation of Solid-State Fermentation Conditions from Pineapple Peel Waste for Release of Bioactive Compounds by Aspergillus niger spp.

Currently, agroindustrial waste can be used to obtain bioactive compounds. The solid-state fermentation is an alternative for the valorization of these waste and to be able to release bioactive compounds that may be of interest to different industrial sectors. The aim of this study was to evaluate solid-state fermentation conditions using pineapple peel waste as the substrate with Aspergillus niger spp., to release bioactive compounds using a Plackett–Burman exploratory design. Temperature, humidity, inoculum, NaNO3, MgSO4, KCl, and KH2PO4 conditions in the fermentation process were evaluated. The antioxidant capacity was determined, and the main compounds of the fermentation extracts were identified. The results revealed that the Aspergillus niger HT3 strain reached a hydrolyzable tannin release of 10.00 mg/g, While Aspergillus niger Aa20 reached a condensed tannin release of 82.59 mg/g. The KH2PO4 affects the release of condensed tannins with A. niger Aa20, and MgSO4 affects the release of hydrolyzable tannins with A. niger HT3. In addition, a positive antioxidant activity was demonstrated for the DPPH, ABTS, and FRAP technique. The main compounds in the fermented pineapple peel were 3-feruloylquinic acid, caffeic acid, lariciresinol, and 3-hydroxyphloretin 2′-O-xylosyl-glucoside, among others. The solid-state fermentation process is a biotechnological alternative for the release of bioactive compounds.

Optimization of Solid-State Fermentation Conditions With Mixed Strains Using Box-Behnken Design for the Production of brewers’ Spent Grain Protein

As the most abundant by-product of the brewing industry, the valorization of proteins from brewers’ spent grains (BSG) is critical to reducing processing waste and meeting the growing demand for plant-derived protein globally. However, the applicability of brewers’ spent grain proteins in food manufacturing has been constrained by the high extraction cost and undesirable functionalities. In this research, BSG was used as the substrate to ferment with the mixed strains Bacillus subtilis, Saccharomyces cerevisiae, and Kluyveromyces marxianus and then subjected to protein extraction. The solid-state fermentation (SSF) conditions were optimized using single-factor tests together with Box-Behnken Design to 50% initial moisture content, 10% strain inoculum ratio, fermented at pH 5.8 under 32 °C for 6 days, with the highest soluble protein concentration of 0.678 ± 0.0047 µg/µL (equivalent to bovine serum albumin). Furthermore, proteins were extracted from unmalted raw barley grains and BSG control (with a yield of 0.338 ± 0.016 µg/µL and 0.352 ± 0.015 µg/µL, respectively) and then evaluated for their physiochemical characterizations as a comparison of solid-state fermented proteins. The physicochemical attributes of all the intact proteins were similar, except that the fermented samples showed a smaller molecular mass on the SDS-PAGE gel. In conclusion, these results indicated that SSF is a feasible strategy for the bioconversion of BSG into valuable food ingredients as it enhances protein extraction efficiency while reducing the production cost, thereby being beneficial to alleviate the associated environmental pollution and to broaden its possibilities for further integration into the circular economy.

Optimization of Solid-State Fermentation Conditions for Enhancing the Nutrition Contents in Tomato Pomace Using RSM

Optimization of Solid-State Fermentation Conditions for Enhancing the Nutrition Contents in Tomato Pomace Using RSM

Determination of tannin acyl hydrolase activity of Streptomyces mirabilis TBGS10 by measuring gallic acid using high-pressure liquid chromatography

Tannase is a hydrolytic enzyme known as tannin acyl hydrolase that acts on the ester bonds of hydrolyzable tannins and produces gallic acid. Tannase enzymes are obtained from various sources. Tannase from microbial sources, especially fungi like Aspergillus spp., has been used in the food, brewing, and pharmaceutical industries. Tannin acyl hydrolase activities of Actinomycetes are seldom reported, though they are known to produce a wide range of industrial enzymes. This communication deals with the tannase activity of a Streptomyces isolate from the shola forests of Munnar in the Western Ghats of Kerala. The isolate is identified as S. mirabilis TBGS10 based on morphological characters and 16s rDNA homology. The isolate showed promising tannase activity in plate assays, submerged, and solid-state fermentation conditions. High-pressure liquid chromatography determines the industrially important intermediate gallic acid produced through solid-state fermentation using cashew apple bagasse as substrate. The extract observed a gallic acid (GA) content of 142.624 g/mL with a retention time of 2.506 min. The tannase gene of the strain TBGS10 was PCR amplified using specific primers designed based on similar Streptomyces sequences available in the NCBI-GenBank

Process development for fungal cellulase production and enzymatic saccharification of Parthenium hysterophorus for bioethanol production

Parthenium hysterophorus (PH), often known as parthenium weed, is one of the seventh most devastating weeds in the world.The primary aim of the study was to produce and optimize fungal FPase enzymes under solid-state fermentation (SSF) conditions for application in enzymatic hydrolysis to produce bioethanol. The impact of various physiological factors was verified through a systematic approach, initially using the one-factor-at-a-time (OFAT) method. Further optimization was carried out using statistical tools by response surface methodology (RSM), selecting three variables, i.e., lactose concentration, peptone concentration, and pH level. The outcomes of this research demonstrated that the RSM-based model led to the optimization of enzyme activity, resulting in 4.08U/ml of FPase, with a lactose concentration of 1.62 %, a peptone concentration of 1.5 %, and a pH level of 6 being the ideal conditions. When employing the FPase enzyme for biomass hydrolysis, the maximum yield of reducing sugar, at 0.37 ± 0.01 g/g, was achieved within a 96-hour period, using enzyme and substrate levels of 30 FPU/100 ml and 3 % (w/v), respectively. Fermentation of enzymatic hydrolysate was carried out by Saccharomyces cerevisiae at 30 °C, pH 6.0, and 120 rpm, which resulted in 0.45g/g ethanol yield after 48 h. Overall, our findings reveal thatPH biomass can be introduced into sugar-based biorefineries to produce biofuels and other valuable chemicals.

Versatile Applications of Brewer's Spent Grain: Solid-State Fermentation and Nutritional Added Value.

Brewer's spent grain (BSG) is a major by-product in the beer-brewing process which contributes to 85% of the entire generated by-product in the brewing process. BSG is rich in proteins, and most of the malt proteins (74-78%) remain insoluble in BSG after the mashing process. Solid-state fermentation (SSF) is a promising bioprocess that enables microorganisms to survive in environments with minimal water and has shown to enhance the nutritional composition of BSG. In this review, the potential application of protein, amino acids (proline, threonine, and serine), phenolic contents, and soluble sugars (glucose, fructose, xylose, arabinose, and cellobiose) extracted from BSG by various microorganisms using SSF is explored. Incorporation of BSG into animal feed, human diets, and as a substrate for microorganisms are the prospects that could be implemented in the industrial scale. This review also discussed various advances to improve the fermentation yield such as symbiotic fermentation, the addition of nitrogen supplements, and an optimal mixture of the agro-industrial waste substrate. Future perspectives on SSF are also addressed to provide important ideas for immediate and future studies. However, challenges include optimizing SSF conditions and design of bioreactors, and operational costs must be addressed in the future to overcome current obstacles. Overall, this mini review highlights the potential benefits of BSG utilization and SSF in a sustainable way.

Purification and characterization of extracellular tannase from Aspergillus fumigatus MA using Syzigium cumini leaves under solid state fermentation

This study reports the tannase purification produced by a tannery effluent-originated fungal isolate i.e., Aspergillus fumigatus MA under solid state fermentation (SSF) condition. Purification of tannase from culture filtrate was attained using ammonium sulfate precipitation with subsequent diethylaminoethyl (DEAE)-cellulose mediated ion exchange chromatographic technique. Fractional precipitation of the culture filtrate with 60–80% ammonium sulfate yielded 80.9% recovery of tannase with 6.16-fold purification. The enzyme fractions were collected and eluted as a single peak using 0.5 M NaCl-gradient concentration. DEAE-cellulose column chromatography results in overall 23-fold purification with 27.6% recovery of the enzyme. SDS-PAGE analysis of purified tannase confirmed the presence of a single band of protein with a molecular mass equivalent to 66.2 kDa. The highest activity of tannase was observed at optimum pH ranged between 5.0–6.0 whereas, the tannase stability (>80%) was observed at 4.0 to 7.0 pH ranges. The purified tannase activity was found to be optimally active at 30 °C whereas stability (>90%) was accomplished between 30–50 °C temperature. The Km and Vmax were found to be 1.61 × 10−3 M and 1.04 mM respectively. These properties suggest the potential of the enzyme to be utilized in various food, feed, and pharmaceutical sectors.

Decolorization of Textile Azo Dye via Solid-State Fermented Wheat Bran by Lasiodiplodia sp. YZH1.

Textile dyes are one of the major water pollutants released into water in various ways, posing serious hazards for both aquatic organisms and human beings. Bioremediation is a significantly promising technique for dye decolorization. In the present study, the fungal strain Lasiodiplodia sp. was isolated from the fruiting bodies of Schizophyllum for the first time. The isolated fungal strain was examined for laccase enzyme production under solid-state fermentation conditions with wheat bran (WB) using ABTS and 2,6-Dimethoxyphenol (DMP) as substrates, then the fermented wheat bran (FWB) was evaluated as a biosorbent for Congo red dye adsorption from aqueous solutions in comparison with unfermented wheat bran. A Box-Behnken design was used to optimize the dye removal by FWB and to analyze the interaction effects between three factors: fermentation duration, pH, and dye concentration. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were applied to study the changes in the physical and chemical characteristics of wheat bran before and after fermentation. An additional experiment was conducted to investigate the ability of the Lasiodiplodia sp. YZH1 to remove Congo red in the dye-containing liquid culture. The results showed that laccase was produced throughout the cultivation, reaching peak activities of ∼6.2 and 22.3 U/mL for ABTS and DMP, respectively, on the fourth day of cultivation. FWB removed 89.8% of the dye (100 mg L-1) from the aqueous solution after 12 h of contact, whereas WB removed only 77.5%. Based on the Box-Behnken design results, FWB achieved 93.08% dye removal percentage under the conditions of 6 days of fermentation, pH 8.5, and 150 mg L-1 of the dye concentration after 24 h. The fungal strain removed 95.3% of 150 mg L-1 of the dye concentration after 8 days of inoculation in the dye-containing liquid culture. These findings indicate that this strain is a worthy candidate for dye removal from environmental effluents.

Optimization of fermentation conditions to improve the functional and structural characteristics of rapeseed meal with a mutant Bacillus subtilis species

This investigation aimed to provide the optimum solid-state fermentation (SSF) conditions to enhance the functional and structural characteristics of rapeseed meal (RM). Response Surface Methodology (RSM) was used to optimize the experimental fermentation conditions (temperature, incubation time, and inoculum size) on the protease activity, peptide content, and DPPH activity of RM with Central Composite Design (CCD). The quadratic models of the investigated responses were developed, and their coefficients were observed from the multiple-regression analysis. ANOVA indicated that incubation time was highly significant (p < .01) in all experimental responses. The optimized fermentation conditions of protease activity, peptide content, and DPPH activity were accessed at 92 h, 44 °C, and 8 mL, and the predicted data for these responses were 212.59 U/g, 192.35 mg/g, and 93.46%, respectively. The verification experiment indicated that the measured values of the three responses were insignificant (p > 0.05) with the predicted results, suggesting that the CCD model was fittingly used in predicting such responses. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy outcomes showed remarkable alteration in RM morphology, surface topography, and secondary conformation after 92 h of fermentation. Correlational analysis indicated that β-turn had a strong interrelationship with the functional properties (i.e., DPPH, total phenol content, and Emulsifying properties) of FRM. The improved parameters obtained displayed their effectiveness in improving the bioactive and structural properties of FRM.

Cleavage of macromolecule (protein/polysaccharide)-phenolic bond in soybean cell wall through Lactobacillus casei and Lactobacillus helviticus mixed culture solid-state fermentation for chlorogenic acid extraction

Out of the available dietary sources use for chlorogenic acid extraction, soybean is new and cheap that could offer cost-effective chlorogenic acid production under solid-state fermentation (SSF). Consequently, the study aimed at investigating the cleavage of protein/carbohydrate-phenolic bond in heilong48 soybean (HS) variety via solid-state fermentation by Lactobacillus casei and Lactobacillus helviticus mixed culture for chlorogenic acid extraction with high yield and increased biological activity. A simplistic two-pot bioproduct optimization approach was used; first, screening (Plackett-Burman design) of SSF conditions and second, optimizing (Box-Behnken design) the significant SSF conditions obtained from the former design. The liquid-solid (liquid:solid) ratio of 32:68 (0.47), incubation time of 48 h, pH of 5, and temperature of 50 °C were the best-optimized SSF conditions obtained from the chronological combinatory screening and optimization methods. These conditions gave a satisfactory SSF model, and correspondingly acceptable chlorogenic acid yield (9.20 ± 0.17 mg/g), fermentation efficiency (37.26 ± 0.73%), and 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging activity (DPPH) (65.21 ± 2.05 μmol AA eq/g dry sample) results. The L. casei and L. helviticus mixed culture fermented heilong48 soybean (MCFHS) sample (under optimized SSF conditions) had high (p < 0.05) chlorogenic acid yield and 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging activity than the raw heilong48 soybean flour (RHSF) sample. The effectiveness of the optimized solid-state fermentation conditions on the structural modifications of heilong48 soybean sample was confirmed by scanning electron microscopy, atomic force microscopy, and Fourier transform infrared results.

Inulinase and fructooligosaccharide production from carob using Aspergillus niger A42 (ATCC 204447) under solid-state fermentation conditions

This study aimed to the production of inulinase and fructooligosaccharides (FOSs) from carob under the solid-state fermentation (SSF) conditions by using Plackett-Burman Design (PBD). Based on the results the maximum inulinase and specific inulinase activities were 249.98 U/mL and 318.29 U/mg protein, respectively. When the fructooligosaccharide (FOS) results were evaluated, the maximum values of 1,1,1-Kestopentaose, 1,1-Kestotetraose, and 1-Kestose were 182.01, 506.16, 132.16 ppm while the lowest and highest total FOS values were 179.35 and 516.66 ppm, respectively. On the other hand, it was observed that the maximum inulinase activity was found at the center points of the design. Therefore, validation fermentations were carried out at center point conditions. Subsequently, the yielded bulk enzyme extracts were partially purified using Spin-X UF membranes with 10, 30, and 50 kDa cut-off values. After purification, the maximum inulinase activity was 247.30 U/mg using a 50 kDa cut-off value. Followed by this process, the purified enzyme was used to produce FOSs and the results indicated that the maximum total FOS amount was 28,712.70 ppm. Consequently, this study successfully demonstrates that Aspergillus niger A42 inulinase produced from carob under the SSF conditions can be used in FOSs production.

Novel Transcription Factor CXRD Regulates Cellulase and Xylanase Biosynthesis in Penicillium oxalicum under Solid-State Fermentation.

Penicillium oxalicum produces an integrated, extracellular cellulase and xylanase system, strictly regulated by several transcription factors. However, the understanding of the regulatory mechanism of cellulase and xylanase biosynthesis in P. oxalicum is limited, particularly under solid-state fermentation (SSF) conditions. In our study, deletion of a novel gene, cxrD (cellulolytic and xylanolytic regulator D), resulted in 49.3 to 2,230% enhanced production of cellulase and xylanase, except for 75.0% less xylanase at 2 days, compared with the P. oxalicum parental strain, when cultured on solid medium containing wheat bran plus rice straw for 2 to 4 days after transfer from glucose. In addition, the deletion of cxrD delayed conidiospore formation, leading to 45.1 to 81.8% reduced asexual spore production and altered mycelial accumulation to various extents. Comparative transcriptomics and real-time quantitative reverse transcription-PCR found that CXRD dynamically regulated the expression of major cellulase and xylanase genes and conidiation-regulatory gene brlA under SSF. In vitro electrophoretic mobility shift assays demonstrated that CXRD bound to the promoter regions of these genes. The core DNA sequence 5'-CYGTSW-3' was identified to be specifically bound by CXRD. These findings will contribute to understanding the molecular mechanism of negative regulation of fungal cellulase and xylanase biosynthesis under SSF. IMPORTANCE Application of plant cell wall-degrading enzymes (CWDEs) as catalysts in biorefining of lignocellulosic biomass into bioproducts and biofuels reduces both chemical waste production and carbon footprint. The filamentous fungus Penicillium oxalicum can secrete integrated CWDEs, with potential for industrial application. Solid-state fermentation (SSF), simulating the natural habitat of soil fungi, such as P. oxalicum, is used for CWDE production, but a limited understanding of CWDE biosynthesis hampers the improvement of CWDE yields through synthetic biology. Here, we identified a novel transcription factor CXRD, which negatively regulates the biosynthesis of cellulase and xylanase in P. oxalicum under SSF, providing a potential target for genetic engineering to improve CWDE production.

Production and Characterization of Cellulase Enzyme Produced by Bacillus Isolates from Different Sources

This study was conducted to produce and characterize cellulaseenzymes from Bacillus isolates and to determine the optimum conditionsfor cellulase activity. Four Bacillus isolates were used: iso 9+ fromcompost and iso13, iso23 and iso20 from soil. The four isolates (9+, 23,13 and 20) gave average cellulase activities of 2.89, 3.12, 3.48 and 3.53Unit/ml, respectively. The pH optimum for cellulases from the fourisolates was 6, and the temperature optima were 45, 60, 60 and 80°C,respectively. Cellulases from isolates 13 and 23 were more thermostableand retained 40.2% and 21.9% of their initial activities after incubationfor 110 min at 90°C. Cellulase was produced under solid statefermentation conditions in maize cobs, sorghum stover or bagassepretreated with 2% hydrochloric acid from the above four isolates as wellas from two more isolates (iso4- and iso2-) which were isolated from cowdung. Maximum cellulase activity was 3.78 Unit/ml from isolate 4- usingbagasse and maize cobs as substrate. These results demonstrated thatBacillus isolates 13, 23, 20 and 9+ produced active thermostableextracellular cellulase. Bagasse and maize cobs are suitable as substraesfor production of the enzyme cellulase under solid state fermentation.

Rice straw derived graphene-silica based nanocomposite and its application in improved co-fermentative microbial enzyme production and functional stability

Cellulases are the one of the most highly demanded industrial biocatalysts due to their versatile applications, such as in the biorefinery industry. However, relatively poor efficiency and high production costs are included as the key industrial constraints that hinder enzyme production and utilization at economic scale. Furthermore, the production and functional efficiency of the β-glucosidase (BGL) enzyme is usually found to be relatively low among the cellulase cocktail produced. Thus, the current study focuses on fungi-mediated improvement of BGL enzyme in the presence of a rice straw-derived graphene-silica-based nanocomposite (GSNCs), which has been characterized using various techniques to analyze its physicochemical properties. Under optimized conditions of solid-state fermentation (SSF), co-fermentation using co-cultured cellulolytic enzyme has been done, and maximum enzyme production of 42 IU/gds FP, 142 IU/gds BGL, and 103 IU/gds EG have been achieved at a 5 mg concentration of GSNCs. Moreover, at a 2.5 mg concentration of nanocatalyst, the BGL enzyme showed its thermal stability at 60°C and 70 °C by holding its half-life relative activity for 7 h, while the same enzyme demonstrated pH stability at pH 8.0 and 9.0 for the 10 h. This thermoalkali BGL enzyme might be useful for the long-term bioconversion of cellulosic biomass into sugar.

PRODUCTION OF LACCASE FROM GANODERMA SP. BY USING AGRO-RESIDUAL WASTES

Solid-state fermentation (SSF) has emerged as a potential technology for the production of microbial products such asfeed, fuel, food, industrial chemicals and pharmaceutical products. Its application in bioprocesses such as bioleaching, biobeneficiation, bioremediation, biopulping, etc. has offered several advantages. Utilisation of agro-industrial residues assubstrates in SSF processes provides an alternative avenue and value-addition to these otherwise under- or non-utilisedresidues. The aim of this study was to determine the most promising fungus, the best solid substrate and the optimalconditions for the production of laccase. A laccase producing fungus Ganoderma sp. was isolated and produces laccase byutilizing the agro-wastes. The study revealed that the rice bran was found to be the best supported lignocellulosicsubstrate for extracellular laccase production under SSF and optimum condition for highest lacacse activity of pH andtemperature were observed at 6.0 and 45°C respectively. The incubation periods for laccase maximum activity was at 8thday. Glucose and Peptone were the best supported carbon and nitrogen source for the maximum laccase activity.

Solid-State Fermentation of Plant Feedstuff Mixture Affected the Physiological Responses of European Seabass (Dicentrarchus labrax) Reared at Different Temperatures and Subjected to Salinity Oscillation.

This study aimed to evaluate the effects of dietary inclusion of plant feedstuff mixture (PFM) pre-treated by solid-state fermentation (SSF) on the physiological responses of European seabass. For that purpose, two diets were formulated to contain: 20% inclusion level of non-fermented plant ingredients mixture (20Mix) and 20Mix fermented by A. niger in SSF conditions (20Mix-SSF). Seabass juveniles (initial body weight: 20.9 ± 3.3 g) were fed the experimental diets, reared at two different temperatures (21 and 26 °C) and subjected to weekly salinity oscillations for six weeks. Growth performance, digestive enzyme activities, humoral immune parameters, and oxidative stress indicators were evaluated. A reduction in weight gain, feed intake, and thermal growth coefficient was observed in fish fed the fermented diet (20Mix-SSF). Salinity oscillation led to an increase in weight gain, feed efficiency, daily growth index, and thermal growth coefficient, regardless of dietary treatment. Higher rearing temperatures also increased daily growth index. No dietary effect was observed on digestive enzymes activities, whereas rearing temperature and salinity oscillation modulated digestive enzyme activities. Oxidative stress responses were significantly affected by experimental diets, temperature, and salinity conditions. Catalase and glutathione peroxidase activities showed an interactive effect. Fish reared at 21 °C showed higher enzymatic activity when fed the 20Mix-SSF. Conversely, fish reared at 26 °C showed higher GPx activity when fed the 20Mix diet. Fish reared at 26 °C showed reduced peroxidase and lysozyme activities, while salinity fluctuation led to increased lysozyme activity and decreased ACH50 activity. ACH50 activity increased in fish fed the 20Mix-SSF. Overall, the dietary inclusion of PFM fermented by A. niger was unable to mitigate the impact of environmental stress on physiological performance in European seabass. In fact, fermented feed caused an inhibition of growth performances and an alteration of some physiological stress indicators.