Solid-state Fermentation Process Research Articles

Optimising the recovery of phenolic compounds and antioxidant activity from orange peels through solid-state fermentation

It is widely recognised that orange peels contain a considerable quantity of phenolics, primarily in the form of glycosides. The process of fermentation holds potential as a viable method for extracting phenolic compounds and facilitating their biotransformation into novel metabolites. The aim of this study was to assess the enhanced release of phenolic compounds through the process of solid-state fermentation of orange peels using microorganisms. Following a 6-day incubation period, the methanol extract obtained from the sample fermented with starter Banh men exhibited the highest concentration of total phenolic compounds (17.57 ± 0.34 mg GAE/g DW) and demonstrated the most significant DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity (55.03%). The Reverse Phase High Performance Liquid Chromatography (RP-HPLC) analysis revealed that the predominant phenolic compounds in all fermented samples were flavonoid aglycones, specifically naringenin, hesperetin, and nobiletin. Conversely, in the unfermented orange peels, the major compound observed was the glycoside derivative hesperidin.

Optimization and Detergent Compatibility of Protease Produced from Aspergillus oryzae by Utilizing Agro Wastes.

The biotechnological process called solid-state fermentation (SSF) was applied for hyper production of protease by using a fungal strain called Aspergillus oryzae. From screening of 9 different local substrates (peanut shell, wheat bran, guava leaves, sugar cane bagasse, rice polish, wheat straw, corn straw, reed grass, and rice straw), peanut shells serve as the best substrates for protease production under optimized cultured conditions. The varying physiochemical parameters such as pH (2-9.5), temperature (30-52 °C), incubation time (1-10 days), inoculum size (1-8 mL), moisture level (20-125%), and substrate concentration (1-7 g) were optimized by response surface methodology (RSM). The highest activity of protease was recorded to be 1101.778 U/mL at 660 nm using peanut shell was optimum at pH 8, temperature 52 °C, incubation time 8 days, inoculum size 2 mL, moisture level 20%, and substrate concentration 2 g. The crude form of enzymes produced were further purified through ammonium sulfate precipitation, dialysis, and gel filtration chromatography. Then, purified enzymes were characterized at different pH, temperature, and incubation time. For characterization of purified protease, pH, temperature, and incubation time were 8, 52 °C, and 8 days for peanut shell and was done by one factor at a time method. Hence, isolated enzymes were alkaline in nature, i.e., alkaline proteases. Then, protease produced from peanut shells was applied to locally available detergents to increase their catalytic activity for strain removal. At last, the final results were interpreted in the form of 3D surface and contour plots using Microsoft Excel 2013 and Minitab 17 software. In conclusion, the utilization of A. oryzae and peanut shell as the substrate in the biotechnological process of SSF demonstrated successful hyper production of alkaline protease. The optimized conditions resulted in high enzyme activity and showcased the potential application of the isolated enzymes in improving the catalytic activity of locally available detergents.

Biphasic Fermentation of Trapa bispinosa Shells by Ganoderma sinense and Characterization of Its Polysaccharides and Alcoholic Extract and Analysis of Their Bioactivity.

Trapa bispinosa shells (TBs) and its flesh (TBf) have been recognized for their medicinal properties, including antioxidant, antitumor, and immunomodulatory effects. Despite these benefits, TBs are often discarded as waste material, and their applications remain to be further explored. In this study, we optimized the solid-state fermentation process of Ganoderma sinense (GS) with TBs using a response surface experiment methodology to obtain the fermented production with the highest water extract rate and DPPH free radical scavenging activity. We prepared and characterized pre-fermentation purified polysaccharides (P1) and post-fermentation purified polysaccharides (P2). Alcoholic extracts before (AE1) and after (AE2) fermentation were analyzed for active components such as polyphenols and flavonoids using UPLC-QTOF-MS/MS (ultra-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry). Mouse macrophages (RAW 264.7) were employed to compare the immune-stimulating ability of polysaccharides and the antioxidant activity of AE1 and AE2. Optimal fermentation conditions comprised a duration of 2 days, a temperature of 14 °C, and a humidity of 77%. The peak water extract yield and DPPH free radical scavenging rate of the water extract from TBs fermented by GS were observed under these conditions. The enhanced activity may be attributed to changes in the polysaccharide structure and the components of the alcoholic extract. The P2 treatment group indicated more secretion of RAW 264.7 cells of NO, iNOS, IL-2, IL-10, and TNF-α than P1, which shows that the polysaccharides demonstrated increased immune-stimulating ability, with their effect linked to the NF-кB pathway. Moreover, the results of the AE2 treatment group indicated that secretion of RAW 264.7 cells of T-AOC and T-SOD increased and MDA decreased, which shows that the alcoholic extract demonstrated enhanced antioxidant activity, with its effect linked to the Nrf2/Keap1-ARE pathway. Biphasic fermentation of Trapa bispinosa shells by Ganoderma sinense could change the composition and structure of the polysaccharides and the composition of the alcoholic extract, which could increase the products' immunomodulatory and antioxidant activity.

Optimization of Solid-State Fermentation Process of Radix Ranunculi ternate Using Response Surface Method and Addressing Its Antioxidant and Hypoglycemic Activity

Objective: The aim of this study was to optimize the fermentation process of Radix Ranunculi ternate via microbial fermentation and analyze the changes in the contents of the main components, the antioxidant and hypoglycemic capacities of the extract before and after fermentation. Methods: The solid-state fermentation process was optimized using single-factor tests and the response surface method, with the yield of the alcohol extract of R. ternate as an evaluation index. Results: The best fermentation process was optimized using solid-state endophytic fungus fermentation technology as follows: strain addition ratio of Chaetomium globosum/Fusarium equiseti = 1:1, fermentation for 5 d, sieve size of 40 mesh, liquid/material ratio of 0.8:1 mL·g−1, fermentation temperature of 31 °C, and inoculation amount of 7.5%. Under the optimized conditions, the contents of the water-soluble extract and total polysaccharides decreased by 12.71% and 12.95%, respectively. In the fermentation, the contents of the ethanol-soluble extract, flavonoids, saponins, polyphenols, organic acids, and total amino acids of the fermented R. ternate increased by 19.77%, 57.14%, 79.67%, 14.29%, 17.63%, and 3.82%, respectively. The scavenging rate for DPPH, ABTS+, and ·OH free radicals and inhibitory rate for α-amylase of the fermented R. ternate also increased by 19.02%, 14.17%, 7.53%, and 34.54%, respectively, compared with the unfermented R. ternate. Conclusions: Solid-state fermentation opens new avenues for the development and application of R. ternate as a natural antioxidant and hypoglycemic food.

Optimization of Fermentation Conditions for 2,3,5-Trimethylpyrazine Produced by Bacillus amyloliquefaciens from Daqu

2,3,5-trimethylpyrazine (TMP), as a volatile heterocyclic nitrogen compound, has a wide range of applications. To explore an efficient and environmentally friendly way to produce TMP, Bacillus strains were isolated from Daqu using traditional separation and purification methods. The fermentation products were detected by gas chromatography–mass spectrometry (GC-MS), and the species relationship of strains was analyzed by morphological and phylogenetic tree construction. Single factors were selected to optimize the fermentation process of TMP production, and a Box–Behnken design was used for response surface testing. The LC-6 strain isolated from Daqu was Bacillus amyloliquefaciens, and its fermentation products contained TMP, with a relatively high value of 0.071 ± 0.011 mg/g, indicating that the LC-6 strain was a potentially valuable TMP-producing bacterium. The results of single-factor testing showed that temperature, bottle capacity, and water addition significantly affected TMP production. Box–Behnken design and response surface analysis revealed that the order of influence on TMP yield was as follows: water addition > temperature > bottle capacity. Response surface optimization results showed that the optimal parameters for wheat medium fermentation were temperature 37 °C, bottle capacity 100 g/250 mL, and water addition 39 mL. Under these fermentation conditions, the average production of TMP was 0.446 ± 0.052 mg/g, which was 0.375 mg/g higher than that obtained before optimization. Compared with the previous period, the production of TMP indeed increased, providing a basis for further research on the solid-state fermentation process of TMP synthesis.

Bioprocessing of Epothilone B from Aspergillus fumigatus under solid state fermentation: Antiproliferative activity, tubulin polymerization and cell cycle analysis

Epothilone derivatives have been recognized as one of the most powerful anticancer drugs towards solid tumors, for their unique affinity to bind with β-tubulin microtubule arrays, stabilizing their disassembly, causing cell death. Sornagium cellulosum is the main source for Epothilone, however, the fermentation bioprocessing of this myxobacteria is the main challenge for commercial production of Epothilone. The metabolic biosynthetic potency of epothilone by Aspergillus fumigatus, an endophyte of Catharanthus roseus, raises the hope for commercial epothilone production, for their fast growth rate and feasibility of manipulating their secondary metabolites. Thus, nutritional optimization of A. fumigatus for maximizing their epothilone productivity under solid state fermentation process is the objective. The highest yield of epothilone was obtained by growing A. fumigatus on orange peels under solid state fermentation (2.2 μg/g), bioprocessed by the Plackett-Burman design. The chemical structure of the extracted epothilone was resolved from the HPLC and LC-MS/MS analysis, with molecular mass 507.2 m/z and identical molecular fragmentation pattern of epothilone B of S. cellulosum. The purified A. fumigatus epothilone had a significant activity towards HepG2 (IC50 0.98 μg/ml), Pancl (IC50 1.5 μg/ml), MCF7 (IC50 3.7 μg/ml) and WI38 (IC50 4.6 μg/ml), as well as a strong anti-tubulin polymerization activity (IC50 0.52 μg/ml) compared to Paclitaxel (2.0 μg/ml). The effect of A. fumigatus epothilone on the immigration ability of HepG2 cells was assessed, as revealed from the wound closure of the monolayer cells that was estimated by ~ 63.7 and 72.5%, in response to the sample and doxorubicin, respectively, compared to negative control. From the Annexin V-PI flow cytometry results, a significant shift of the normal cells to the apoptosis was observed in response to A. fumigatus epothilone by ~ 20 folds compared to control cells, with the highest growth arrest of the HepG2 cells at the G0-G1 stage.

The process of solid-state fermentation of soybean meal: antimicrobial activity, fermentation heat generation and nitrogen solubility index.

Bacillus amyloliquefaciens has excellent protease production ability and holds great prospects for application in the solid-state fermentation of soybean meal (SBM). Among eight strains of bacteria, Bacillus amyloliquefaciens subsp. plantarum CICC 10265, which exhibited higher protease production, was selected as the fermentation strain. The protease activity secreted by this strain reached 106.41 U mL-1 . The microbial community structure differed significantly between natural fermentation and inoculation-enhanced fermented soybean meal (FSBM), with the latter showing greater stability and inhibition of miscellaneous bacterial growth. During fermentation, the temperature inside the soybean meal increased, and the optimal environmental temperature for FSBM was found to be between 35 and 40 °C. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and nitrogen solubility index (NSI) results demonstrated that solid-state fermentation had a degrading effect on highly denatured proteins in SBM, resulting in an NSI of 67.1%. Bacillus amyloliquefaciens subsp. plantarum CICC 10265 can enhance the NSI of SBM in solid-state fermentation and inhibit the growth of miscellaneous bacteria. © 2023 Society of Chemical Industry.

Impact of solid-state fermentation utilizing Saccharomyces boulardii on the chemical composition and bioactive constituents of rice husk

The objective of this study was to evaluate the effect of solid-state fermentation, utilizing Saccharomyces boulardii on brown rice husk, black rice husk, and smoked rice husk substrates in terms of the availability of different compounds. The fermentation process was carried out at 37 °C for a maximum of 12 h, using yeast (2.5 % w/w) and water (25 %). During fermentation, black rice husks (BLRH) exhibited an increase in vitamins, protein, and fiber content, whereas brown rice husks (BRRH) showed an increase in carbohydrate and fiber, and smoked rice husks (SRH) decreased lipid and fiber content. The solid-state fermentation process also enhanced the availability and accessibility of minerals, except for smoked rice husk. The levels of phenolic compounds in fermented black, brown, and smoked rice husks were 1165, 1108, and 1051 μg per gram of sample, respectively. Importantly, black rice husk fermented for 8 h demonstrated the most favorable results in terms of nutrient and bioactive compound availability. Principal Component Analysis (PCA) revealed correlations among the variables, which could be manipulated to improve the accessibility of diverse compounds.

Statistical optimization of process variables for anti-hypercholesterolemic metabolites production from Monascus purpureus MTCC 369 fermented finger millet

Monascus purpureus fermented rice has been used for centuries to treat hypercholesterolemia, indigestion, and diarrhea in East Asian countries. Monacolin K, also known as lovastatin, a secondary metabolite synthesized by Monascus sp. in fermentation, is mainly responsible for reducing the level of blood lipids. Besides statins, sterols produced in this process have also been reported to have hypolipidemic effects. In the current study, statin and total sterol production by M. purpureus microbial type culture collection and Gene Bank MTCC 369 on finger millet (FM) substrate were investigated. The central composite design of the response surface methodology (RSM) was used for the optimization of different fermentation process independent variables such as fermentation time period, temperature, inoculum volume, and pH for maximum production of statins and total sterols by M. purpureus MTCC 369. The maximum statin (9.78 mg/g) and sterol (0.46 mg/g) production was achieved at a temperature of 29.44°C, pH 5.0, inoculum size 5.37 ml, and fermentation time of 13.8 days. Fermentation process factors such as fermentation time period and temperature were significant positive factors, while pH and inoculum volume were found to be insignificant factors. The interactive effects of the positively influencing variables have been demonstrated. Compared with the traditional production of these metabolites, using FM as a substrate is promising for the high production of anti-hypercholesterolemic metabolites. The current study was aimed at optimization of the solid-state fermentation process of statin and total sterol using RSM for nutritional FM so as to improve M. purpureus-fermented FM (like red yeast rice) with health-promoting properties. This is the first report on the optimization of statin and sterols from M. purpureus MTCC 369 fermented FM with a significant yield that is on par with that reported so far.

Valorization of agro-industrial wastes using fungi for industrial enzymes production

Huge quantities of the agricultural wastes are produced from practices related to industrial processing, which are mainly burned and thrown in landfills, becoming a threat to the human health and causing environmental pollution. Agro-industrial residues, such as sugarcane bagasse, orange peel, wheat bran, corn straw, barley, rice straw, corn cob, husk, soy bran, and coffee husk were considered as valuable raw materials that can be converted into products of biotechnological interest using microorganisms. Agro-industrial wastes rich in nutrients, such as proteins, minerals, and sugars that, used as possible low cost substrates, for the fungal cultivation, thus considered as an alternative eco-friendly tool for many biological products of economic value, such as enzymes. Fungi organisms are capable of synthesizing a wide range of relevant oxidative and hydrolytic extracellular enzymes, such as peroxidases, laccases, xylanases, and cellulases. The enzymes secreted fungi, are proteins that function as bio-catalysts, responsible for carrying out various biochemical reactions, which applied in food, detergent, cellulose, paper, cosmetics and textile industries, etc. Thus, the replacement of raw materials with lignocellulosic-sources can result in reducing environmental problems and resolving the pollution associated with their disposal, in addition a higher investment will be gained. Therefore, a review was carried out on the important value of agro-industrial wastes, and the cultivation of fungal isolates for economic production of the industrially important enzymes, based on submerged and solid-state fermentation processes, as well as the important application of these enzymes.

Microbial community assembly and chemical dynamics of raw brewers’ spent grain during inoculated and spontaneous solid-state fermentation

Solid-state fermentation (SSF) carried out by microbial bioinoculants is an environmentally friendly technology for the sustainable recovery and valorization of agri-food wastes. Particularly, mesophilic SSF processes allows the production of bio-organic fertilizers enriched with beneficial soil microorganisms. However, the establishment of microbial consortia and the interaction with native waste microbiota still require thoughtful investigations. Here, raw brewers’ spent grain (BSG), the main waste from the brewing industry, was subjected to two mesophilic SSF processes (maximum temperature of 35 °C) carried out by a multi-kingdom microbial bioinoculant and the BSG spontaneous microbiota. After 90 days, both SSF processes led to stable organic soil amendments, as indicated by the C:N ratio (10.00 ± 1.4), pH (6.66 ± 0.09), and DOC (8.45 ± 1.2 mg/g) values. Additionally, the fermented BSG showed a high nitrogen content (42.2 ± 3.4 mg/Kg) and biostimulating activities towardLepidium sativumseeds. The monitoring of microbial communities by high-throughput sequencing of 16S and ITS rRNA indicated that BSG samples were enriched in microbial genera with interesting agronomic applications (i.e.,Devosia, Paenibacillum, Trichoderma, Mucor, etc.). Microbial cross-kingdom network analyses suggested that the microbial assembly of BSG was significantly influenced by the bioinoculant, despite the inoculated microbial genera being able to persist in BSG samples only the first week of SSF. This suggests that the study of microbial interactions between exogenous microbial inoculants and waste resident microbiota is required to optimize SSF processes aimed at the recovery and valorization of unprocessed wastes.

Sustainable valorizing high-protein feather waste utilization through solid-state fermentation by keratinase-enhanced Streptomyces sp. SCUT-3 using a novel promoter

Feather waste, a rich source of proteins, has traditionally been processed through high-temperature puffing and acid-base hydrolysis, contributing to generation of greenhouse gases and H2S. To address this issue, we employed circular economy techniques to recover the nutritional value of feather waste. Streptomyces sp. SCUT-3, an efficient proteolytic and chitinolytic bacterium, was isolated for feather degradation previously. This study aimed to valorize feather waste for feed purposes by enhancing its feather transformation ability through promoter optimization. Seven promoters were identified through omics analysis and compared to a common Streptomyces promoter ermE*p. The strongest promoter, p24880, effectively enhanced the expression of three candidate keratinases (Sep39, Sep40, and Sep53). The expression efficiency of double-, triple-p24880 and sandwich p24880-sep39-p24880 promoters were further verified. The co-overexpression strain SCUT-3-p24880-sep39-p24880-sep40 exhibited a 16.21-fold increase in keratinase activity compared to the wild-type. Using this strain, a solid-state fermentation process was established that increased the feather/water ratio (w/w) to 1:1.5, shortened the fermentation time to 2.5 days, and increased soluble peptide and free amino acid yields to 0.41 g/g and 0.14 g/g, respectively. The resulting has high protein content (90.49 %), with high in vitro digestibility (94.20 %). This method has the potential to revolutionize the feather waste processing industry.

Extraction process, physicochemical properties, and digestive performance of red yeast rice starch.

In the present study, taking red yeast rice (RYR) as the raw material, the optimum extraction process of RYR starch was investigated through a single-factor experiment and the Box-Behnken design: The liquid-to-solid ratio was 5mL/g, the concentration of sodium hydroxide solution was 0.075mol/L, and the extraction time was 3.1h. Under these extraction conditions, the extraction rate of starch reached 90.077%. To explore the influence of solid-state fermentation on RYR starch, three different fermentation stages of RYR starch, raw rice starch, semi-gelatinized rice starch, and RYR starch were used as test materials to determine the changes in the physicochemical properties and glycemic index (GI) values of RYR starch during solid-state fermentation. The results showed that with the advancement of the RYR solid-state fermentation process, the starch particle size gradually increased, the light transmittance gradually decreased, and the solubility and swelling power significantly increased. In addition, the amylose content of starch gradually increased, whereas the amylopectin content gradually decreased; the content of fast digestible starch and slow digestible starch decreased, whereas the content of resistant starch increased. In parallel, during solid-state fermentation, the hydrolysis index significantly decreased, and the GI values also decreased. In summary, solid-state fermentation reduced the digestibility of RYR starch. These results provide a theoretical basis for the structural and physicochemical properties of RYR starch and lay a foundation for its subsequent application and expansion of RYR starch.

Conversion of Corn Stover for Microbial Enzymes Production by Phanerochaete chrysosporium.

Phanerochaete chrysosporium, a white rot fungus, exhibits remarkable capabilities in producing various extracellular enzymes. These microbial enzymes find extensive applications in disrupting the intricate structure of plant cell walls, decolorizing synthetic dyes, and facilitating pulp extraction, among other functions. The process of solid-state fermentation stands out as an economical and sustainable approach, ideal for achieving high yields in enzyme production using lignocellulosic biomass as a substrate. In this research paper, both untreated and alkali pretreated corn stover materials served as substrates for enzyme production, leveraging the fungal strain's capacity to generate enzymes like cellulases and manganese peroxidase. The maximum production of endoglucanase was notably observed, reaching 121.21 ± 0.90 U/gds on the 9th day for untreated biomass and 79.75 ± 0.57 U/gds on the 6th day for treated biomass. Similarly, the peak exoglucanase production was recorded at 2.46 ± 0.008 FPU/ml on the 3rd day for untreated biomass and 0.92 ± 0.002 FPU/ml on the 6th day for treated biomass. Furthermore, the highest production of manganese peroxidase was achieved, with values of 5076.81 U/l on the 6th day for untreated biomass and 1127.58 ± 0.23 U/l on the 3rd day for treated biomass. These results collectively emphasize the potential of corn stover as a renewable and promising substrate for the production of essential enzymes.

Influence of traditional dehulling on mycotoxin reduction and GC-HRTOF-MS metabolites profile of fermented maize products

Contamination with mycotoxins has been a worldwide food safety concern for several decades, and food processing has been suggested as a potential method to mitigate their presence. In this study, the influence of traditional dehulling (TD) on the mycotoxin reduction and metabolites profile of fermented white maize products obtained via natural and three controlled fermentation methods (involving Lactobacillus fermentum, Lactobacillus plantarum, and their mixed cultures) was examined. Gas chromatography coupled with high resolution time-of-flight mass spectrometry (GC-HRTOF-MS) and ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) were employed. TD brought the levels of fumonisin B1 (FB1) and B2 (FB2) in the white maize below the regulatory limit set by the European Union (EU) for maize consumed by humans. While TD increased the concentration of several mycotoxins in the fermented maize products obtained from other studied fermentation methods, it primarily reduced aflatoxin B1 (AFB1), FB1, deoxynivalenol, and 15-acetyldeoxynivalenol in the L. plantarum-fermented products. By tempering the dehulled maize, a solid-state fermentation process began. This was used in TD to make it easier to remove the pericarp. GC-HR-TOF-MS metabolomics revealed that TD brought about the generation of 12 additional compounds in the dehulled maize though some metabolites in the whole maize were lost/biotransformed. The fermented dehulled maize products obtained from the four studied fermentation procedures contained fewer compounds than the fermented whole maize products. Overall, the analysis showed that all fermented maize (whole and dehulled) produced had varied nutritional metabolites and mycotoxin concentrations below the EU maximum level, except for fermented maize obtained from mixed strains (AFB1 + AFB2 > 4.0 g/kg).

Characterization and nutritional valorization of agricultural waste corncobs from Italian maize landraces through the growth of medicinal mushrooms

The research investigates the potential use of maize cobs (or corncobs) from five genotypes, including the B73 inbred line and four locally cultivated landraces from Northern Italy, as substrate for implementing Solid State fermentation processes with four Medicinal Mushrooms (MMs). The corncobs were characterized based on their proximate composition, lignin, phenolics content (both free and bound), and total antioxidant capacity. Among the MMs tested, Pleurotus ostreatus and Ganoderma annularis demonstrated the most robust performance. Their growth was parametrized using Image Analysis technique, and chemical composition of culture samples was characterized compared to that of corncobs alone. In all culture samples, the growth of MMs led to a significant reduction (averaging 40%) in the total phenolics contents compared to that measured in corncobs alone. However, the high content of free phenolics in the cobs negatively impacted the growth of P. ostreatus. The final MM-corncob matrix exhibited reduced levels of free sugars and starch (≤ 2.2% DW, as a sum) and increased levels of proteins (up to 5.9% DW) and soluble dietary fiber (up to 5.0% DW), with a notable trend toward higher levels of β-glucan compared to corncobs alone. This research paves the way for the use of this matrix as an active ingredient to enhance the nutritional value of food preparations.

Valorization of chicken feather waste using recombinant bacillus subtilis cells by solid-state fermentation for soluble proteins and serine alkaline protease production

Feather waste, a by-product of the poultry industry, is rich in proteins, peptides, and amino acids. Improper disposal of feathers can cause environmental pollution. Solid-state fermentation (SSF) is a viable alternative to submerged fermentation due to its simplicity, productivity, and lower cost. The study goal is a biorefinery of chicken feather waste supplemented with wheat bran using a recombinant Bacillus subtilis strain to produce soluble proteins and a serine alkaline protease. Plackett-Burman Design and Central Composite Design were utilized in a statistical-mathematical model to optimize the process. Multi-factorial design optimization resulted in 80 % substrate degradation efficiency, an alkaline protease with dual activities (1423 proteolytic units and 190 keratinolytic units), 214 mg soluble proteins/g substrate, and 87 % model validation. Scaling up the SSF process to 50 g of substrate significantly enhanced the end products of feather biodegradation to 1616 proteolytic units, 2844 keratinolytic units, and 127 mg soluble proteins/g substrate. Aim and scope of the manuscriptThe aim of the present study is to utilize chicken feather waste (alone or supplemented with other materials) through recombinant Bacillus subtilis cells using solid state fermentation (SSF) at a laboratory scale. The plan study provides a promising waste management in the environmental field concerning biodegradation of such recalcitrant keratinous wastes supplemented with agricultural residues via recombinant microorganism. On semi-pilot scale, high production and quality of soluble protein, protease, and keratinase activity were produced according to the statistically optimised first stage fermentation in the laboratory scale. The bioconversion process took place as a major goal to obtain valuable products, with low utilities and energy requirements. Therefore, this will consider as an economically feasible and environmentally friendly alternative. Moreover, this study is considered as first step fermentation for feather waste to pave the road for directing it to a second step fermentation for biogas production and bioenergy generation through bio-electrochemical systems (Manuscript under publication).

Valorization of Prickly Pear Peel Residues (Opuntia ficus-indica) Using Solid-State Fermentation.

Prickly pear peel (Opuntia ficus-indica) residues can be used as a substrate in solid-state fermentation to obtain bioactive compounds. The kinetic growth of some Aspergillus strains was evaluated. A Box-Hunter and Hunter design to evaluate the independent factors was used. These factors were temperature (°C), inoculum (spores/g), humidity (%), pH, NaNO3 (g/L), MgSO4 (g/L), KCl (g/L), and KH2PO4 (g/L). The response factors were the amount of hydrolyzable and condensed tannins. The antioxidant and antimicrobial activity of fermentation extracts was evaluated. Aspergillus niger strains GH1 and HT3 were the best for accumulating tannins. The humidity, inoculum, and temperature affect the release of hydrolyzable and condensed tannins. Treatment 13 (low values for temperature, inoculum, NaNO3, MgSO4; and high values for humidity, pH, KCl, KH2PO4) resulted in 32.9 mg/g of condensed tannins being obtained; while treatment 16 (high values for all the factors evaluated) resulted in 3.5 mg/g of hydrolyzable tannins being obtained. In addition, the fermented extracts showed higher antioxidant activity compared to the unfermented extracts. Treatments 13 and 16 showed low inhibition of E. coli, Alternaria sp., and Botrytis spp. The solid-state fermentation process involving prickly pear peel residues favors the accumulation of condensed and hydrolyzable tannins, with antioxidant and antifungal activity.

Effect of solid‐state fermentation on the protein quality and volatile profile of pea and navy bean protein isolates

AbstractBackground and ObjectivesFermentation has been increasingly used as a “clean” processing technique to modify proteins. The goal of this research was to assess the use of solid‐state fermentation (SSF) by Aspergillus oryzae on pea (pea protein isolate [PPI]) and navy bean protein isolates (NBPI) for different time periods (0–48 or 0−72 h, respectively) and its impact on their nutrition and volatile profile.FindingsThe SSF process resulted in higher total phenolic content and lower protein digestibility, and consequently, the protein quality was reduced for both pulses. The quantity of the volatile compounds initially present in the samples did not change substantially after SSF; however, many new compounds were identified in fermented PPI, which have been reported to have pleasant sensory properties.ConclusionsThe protein quality of PPI or NBPI was not improved by A. oryzae SSF; however, the results suggest the potential for using SSF to positively modify the volatile profile of PPI.Significance and NoveltyThe findings of this research strengthened our knowledge base of fermented pulse ingredients with the use of protein isolates and navy beans, narrowing the somewhat limited gap for fermentation application to high protein substrates.

Dynamic analysis Caffeic acid production driven by the key physicochemical factor and microbial community succession in Baijiu Daqu: A multi-microorganism fermentation of solid-state fermentation system

Daqu is a saccharifying fermenting agent in the solid-state fermentation process of Strong aromatic Baijiu, providing important raw materials, microorganisms and enzymes for the fermentation of Baijiu, however, a little information about organic acids production in Daqu until now. This work analyzed the correlation among microbial community succession, physicochemical factors and caffeic acid-producing metabolic pathways in key fermentation time-point of strong aromatic Baijiu Daqu, and the results showed that the main functional communities of caffeic acid metabolism were Staphylococcus, Klebsiella, Lactobacillus and Pichia, respectively. The correlation results showed that in the fermentation stage of the Daqu, caffeic acid was mainly influenced by miosture and reducing sugar. Co-occurrence network analysis showed that microbial interactions were stronger in days 0–8 than in days 10–27. The PICRUSt2 marker gene sequence was used to predict information on the function and abundance of enzymes related to different fermentation stages of Daqu, and combined with the related enzymes involve in caffeic acid metabolism, the results indicated that the microbial community in the pre-fermentation 0–8 days had the potential to produce caffeic acid. The results provide a theoretical basis for the analysis of the formation mechanism of phenolic acids in the multi-bacterial co-fermentation system of Daqu fermentation.