Solid-state Fermentation Research Articles

Solid-State Fermentation Engineering of Traditional Chinese Fermented Food.

Solid-state fermentation (SSF) system involves solid, liquid, and gas phases, characterized by complex mass and heat transfer mechanisms and microbial complex interactions. The SSF processes for traditional Chinese fermented foods, such as vinegar, soy sauce, and baijiu primarily rely on experience, and most of the operations are replaced by auto machine now. However, there is still a lack of engineering in-depth study of the microbial process of SSF for complete process control. To meet the demands of smart manufacturing and green production, this paper emphasizes the engineering analysis of the mechanisms behind SSF. It reviews the progress in the engineering aspects of Chinese traditional SSF, including raw material pretreatment, process parameter detection, mathematical model construction, and equipment innovation. Additionally, it summarizes the challenges faced during intelligent upgrades and the opportunities brought by scientific and technological advancements, proposing future development directions. This review provides an overview of the SSF engineering aspects, offering a reference for the intelligent transformation and sustainable development of the Chinese traditional SSF food industry.

Effects of Media and Processes on the Aromas of White Truffle Solid-State Fermented Products

This study aimed to formulate a black bean soy sauce using black beans and black rice as media for the solid-state fermentation of white truffle. Various proportions of these media (4:0, 3:1, 2:2, 1:3, and 0:4) were prepared, with methionine concentrations (0, 0.3, 0.6, 0.9, 1.2, and 1.5%) serving as precursors for a 4-week solid-state fermentation to analyze the aroma profiles. GC-MS analysis showed that samples with 1.5% methionine exhibited significantly higher levels of sulfur-containing volatile compounds compared to those without methionine. GC-IMS analysis revealed that a 2:2 ratio of black beans to black rice produced the most enriched aroma. Lower methionine levels improved mycelial growth, with 0.3% methionine yielding the richest aroma components. After fermentation, the white truffle products were sterilized using autoclaving, hot air assisted radio frequency (HARF), and high pressure processing (HPP), followed by freeze drying. GC-IMS analysis showed that HPP samples had an aroma closest to fresh samples, whereas HARF and autoclave resulted in similar aromas. However, 24 h freeze drying significantly diminished the aroma, resulting in no significant difference in aroma among the freeze-dried products treated with different sterilization methods.

Exploring Non-Saccharomyces yeasts from Daqu for beer production

Daqu is an essential component in the solid-state fermentation of Chinese Baijiu, and non-Saccharomyces yeasts from Daqu significantly contribute to the complex flavors in Baijiu. However, the potential of non-Saccharomyces yeasts from Daqu in beer production has remained unexplored. In this study, 80 strains representing 14 non-Saccharomyces yeast species were isolated from various Daqu. These strains were scrutinized for their stress tolerance, flocculation, fermentation performance, and the production of flavor compounds. Subsequently, representative strains were chosen for beer production, and the resulting products from both single- and mixed-strain fermentations underwent sensory evaluation. Toruaspora delbrueckii TD2 exhibited excellent fermentation properties in wort. In compared to US-05, the non-Saccharomyces yeast strains tested significantly increased volatile favor compounds. Notably, the Wickerhamomyces anomalus strain showed a 13.86-fold increase in ethyl acetate production, while the Hanseniaspora osmophila strain displayed a 7-fold increase in phenylethyl acetate production. Co-fermentations of these strains with US-05 did not impact attenuation and ethanol concentration but significantly enhanced aromatic profiles. This study offers valuable insights into the fundamental attributes and brewing potential of non-Saccharomyces yeasts sourced from Daqu, broadening the spectrum of yeast selection for the creation of innovative beers.

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.

Harnessing Packed-Bed Bioreactors’ Potential in Solid-State Fermentation: The Case of Beauveria bassiana Conidia Production

The packed-bed bioreactor is among the most promising reactor configurations for solid-state fermentation. However, the bed thickness poses several limitations involving mass and energy transfer, heat generation, and the homogeneity of the material, hampering its development at the industrial scale. Fungi are among the most promising microorganisms used in this configuration; however, only polypropylene bags and trays are used at the industrial scale. In this work, Beauveria bassiana is used to demonstrate the potential of solid-state fermentation for conidia production. A scale-up from 0.5 L to 22 L is presented, starting with substrate selection, optimization via design of experiments and 22 L batches. The optimized parameters were 70% moisture, 6.5 × 106 conidia mL−1 inoculum concentration, 20 mL min−1 airflow, 25 °C; temperature, and 40 C/N ratio. After optimization, beer draff was chosen as the preferred substrate for scale-up. Air-filled porosity was found to be the key parameter in fungal solid-state fermentation scale-up, establishing values of around 80% as necessary for fungal conidia production when working in a 22 L packed-bed bioreactor. When compared with the tray bioreactor, the packed bed obtained higher conidia production due to its better use of the total reactor volume. Our study harnesses the potential of the packed-bed bioreactor and serves as a base for further scale-up to industrial scale.

Exploring the Impact of Solid-State Fermentation on Fava Bean Flour: A Comparative Study of Aspergillus oryzae and Rhizopus oligosporus.

Fava bean (Vicia faba L.) is a protein-rich pulse with high nutritional value, but its functional and sensory characteristics limit its application in foods. Solid-state fermentation (SSF) can modify the composition of plant proteins, modulate its functionality, and enhance the sensory aspects. In this study, fava bean flour (FB) was fermented with Aspergillus oryzae and Rhizopus oligosporus to produce FBA and FBR, respectively, ingredients with distinct nutritional, functional, and aroma characteristics. The protein content increased by 20% in FBA and 8% in FBR, while fat levels rose more significantly in FBR (+40%). The overall content of fermentable oligo-, di-, mono-saccharides, and polyols (FODMAPs) decreased by 47% (FBA) and 57% (FBR), although polyol production by A. oryzae was observed. SSF improved the nutritional profile of FBA and FBR, with a notable increase in the concentration of essential amino acids observed, and a reduction in most antinutrients, with the exception of trypsin inhibitors. SSF resulted in the formation of aggregates, which increased the particle size and reduced protein solubility. Emulsions prepared with the fermented ingredients separated faster, and the foaming capacity of both FBA and FBR was decreased, but an increase in water-holding capacity was observed. SSF resulted in the production of predominantly savoury-associated aroma compounds, with compounds characteristic of metallic and mouldy aromas reduced. These results indicate the potential of SSF to transform FB with enhanced nutritional value and improved sensory and functional properties.

Solid-state fermentation with Bacillus subtillis co-cultured with probiotic Lactobacillus spp. enhances the bioactive peptides, nutritional and antioxidative potentials of tamarind seed

The effect of natural or controlled solid-state fermentation using single or mixed probiotic strains on the nutritional, bioactive and phytochemical constituents, and antioxidant activities of tamarind seeds was evaluated. Tamarind seeds were subjected to either controlled solid-state fermentation (37 °C, 72 h) using either Bacillus subtilis only or Bacillus subtilis co-cultured with probiotics Lactobacillus spp. (Lactobacillus fermentum, Lactobacillus rhamnosus GG, Lactobacillus brevis, and Lactobacillus delbrueckii) or natural fermentation while unfermented tamarind seeds served as control. The changes in the nutritional composition, peptide content, antioxidative properties (Ferric reducing antioxidant power (FRAP) and DPPH radical scavenging activities) and total viable count of probiotics in fermented tamarind seed were evaluated using standard methods. The peptide content, crude protein, fat, and fibre (100.19 mg/g, 51.35, 9.50 and 5.10%), and FRAP and DPPH (0.55 and 21.60%) in unfermented tamarind seed were significantly (p < 0.05) lower than fermented tamarind seed (271.00–308 mg/g, 12, 62.84–64.02, 12.21–13.11 and 6.01–6.90, and 1.42–2.92 and 26.66–35.70%, respectively), after 72 h of fermentation. The total viable count in the tamarind seed fermented with Bacillus subtilis only was 1.2 × 109 CFU/g while that co-cultured with probiotics ranged from 6 × 108 to 9.9 × 108 CFU/g after 72 h of fermentation. This study showed that a controlled solid-state fermentation using probiotics Lactobacillus co-cultured with Bacillus subtilis can significantly increase the peptide contents, and enhance the nutritional and antioxidant activities of tamarind seed while producing a condiment with significant probiotic potential.

Preparation, characterization, and mechanism of swelling and Cu2+ adsorption by alginate-based beads enhanced with Huangshui polysaccharides

As biomass resources, Huangshui (HS) is a high-yield by-product from the traditional solid-state fermentation of Chinese Baijiu. This study aims to sustainably utilize crude HS polysaccharide (cHSP) to prepare alginate-based beads for promoting Cu2⁺ adsorption in the wastewater and explore the relative mechanism. Sodium alginate/Fe3O4 (Mag-SA) beads were synthesized via Ca2+-induced crosslinking, while Mag-SA-cHSP beads were created by immobilizing cHSP into Mag-SA matrix. The chemical structure, physical properties, and morphology of the beads were analyzed using FTIR, SEM-EDS, XRD, VSM, TGA, Zetasizer, and XPS, respectively. The swelling performance, adsorption ability, kinetic and thermodynamic characteristics, etc. were conducted to better elucidate the mechanism of Cu2⁺ adsorption enhancement by cHSP. Results showed that 1.0 wt% cHSP addition provided a stable three-dimensional structure and enhanced thermal stability, swelling performance, and adsorption ability. The swelling ratio increased from 75.29 g/g to 86.56 g/g after cHSP incorporated into the beads, which was driven by water diffusion and chain relaxation. The Cu2+ adsorption capacity improved from 59.10 mg/g to 67.89 mg/g after cHSP embedded into the beads, which involved ion-exchange, chelation, and electrostatic interaction. Additionally, the beads retained 66%–71% of their initial adsorption capacities after four adsorption-desorption cycles, indicating the possibility of repeated use to reducing costs. This work presents a novel approach to enhancing the utilization value of Huangshui and developing a reusable and efficient material for heavy metal ion removal from wastewater in an eco-friendly manner.

Molecular identification of Shiitake (Lentinula edodes), analysis and production of beta-glucan using beech wood sawdust waste

Lentinula edodes has the ability to grow and produce bioactive compounds on industrial by-products. This study aimed to produce B-glucan of cell wall Shiitake on Beechwood Sawdust (BWS) through a two-step procedure, which included fermentation and B-glucan extraction and purification. Shiitake mushrooms are cultivated by solid-state fermentation (SSF) using the Jamas method to increase the purity of B-glucan. The fermented substrate was first separated and then hydrolyzed by sodium hydroxide (NaOH) (10 M, 1 M), followed by acid hydrolysis extraction. The structure and purity of B-glucan were confirmed by FTIR, NMR, and AFM spectroscopy. The fungus used was molecularly identified by the 18 s rRNA method. Shiitake mushroom was produced by SSF using BWS and high purity β-glucan was extracted from the produced polysaccharide in the amount of 67.33 mg/g. FTIR, NMR, and AFM analyses proved the production of beta-glucan, and based on molecular identification, it was determined that the mushroom used was Lentinula edodes. The results obtained show that SSF is a valuable technology for the production of biomass and polysaccharides by utilizing the strain of L. edodes. To the best of our knowledge, the yield reported is the highest by the strain of L. edodes using SSF.

Valorization of Date By-Products: Enhancement of Antioxidant and Antimicrobial Potentials through Fermentation.

The by-products from three varieties of dates-Mozafati, Sayer, and Kabkab-were subjected to solid-state fermentation using Aspergillus niger alone or in co-culture with Lactiplantibacillus plantarum or Limosilactobacillus reuteri to enhance their phenolic and flavonoid content, along with antioxidant and antimicrobial activities. Solid-state fermentation, being environmentally friendly and cost-effective, is particularly suitable for agricultural residues. Significant increases (p < 0.05) in total polyphenol content (TPC), total flavonoid content (TFC), and antioxidant power were observed post-fermentation, especially under co-culture conditions. The highest TPC (12.98 ± 0.29 mg GA/g) and TFC (1.83 ± 0.07 mg QE/g) were recorded in the co-culture fermentation of by-products from the Mozafati and Sayer varieties, respectively. HPLC analysis revealed changes in polyphenol profiles post-fermentation, with reductions in gallic and ferulic acids and increases in caffeic acid, p-coumaric acid, rutin, quercetin, and kaempferol. FT-IR analysis confirmed significant alterations in polyphenolic functional groups. Enhanced antimicrobial activity was also observed, with inhibition zones ranging from 8.26 ± 0.06 mm for Kabkab to 17.73 ± 0.09 mm for Mozafati. These results suggest that co-culture solid-state fermentation is a promising strategy for valorizing date by-products, with potential applications in nutraceuticals and/or pharmaceutical products and as valuable additives in the food industry.

A novel approach to produce soy protein isolate: Direct enzymatic hydrolysis of high-temperature soybean meal using proteinase produced by microbial solid-state fermentation

This study proposed a novel extraction method for soy protein isolate, which involved solid-state fermentation of high-temperature soybean meal. The proteinases secreted by microorganisms acted on the high-temperature soybean meal, making the SPI easier to extract. The study concludes that Bacillus amyloliquefaciens subsp. plantarum CICC 10265 could be used for solid-state fermentation of soybean meal, and the fermentation effect was good, with a yield of 41.91 % for SPI. Compared to the direct extraction of SPI from high-temperature soybean meal, the yield had increased by 130.19 %. Meanwhile, we also conducted research on the losses during the SPI extraction process. Through experiments, the study identified the patterns of protease activity changes and microbial colony growth during solid-state fermentation of soybean meal by Bacillus amyloliquefaciens subsp. plantarum CICC 10265. It was concluded that extracting SPI after 8 h of fermentation is more suitable. The experimental results indicated that the total amino acid content of SPI extracted from fermented soybean meal was 2.1 % higher compared to SPI extracted from low-temperature soybean meal. The extracted SPI also met the microbial standards.

Effect of Solid-State Fermentation of Hericium erinaceus on the Structure and Physicochemical Properties of Soluble Dietary Fiber from Corn Husk.

Corn husk, a by-product of corn starch production and processing, contains high-quality dietary fiber (DF). Our study compares and analyzes the impact of Hericium erinaceus solid-state fermentation (SSF) on the structure and physicochemical characteristics of soluble dietary fiber (SDF) of corn husks. The study also investigates the kinetics of SSF of H. erinaceus in this process. The scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) results revealed significant structural changes in corn husk SDF before and after fermentation, with a significant elevation in the functional group numbers. The data indicate that the fermented corn husk SDF's water-holding, swelling, and oil-holding capacities increased to 1.57, 1.95, and 1.80 times those of the pre-fermentation SDF, respectively. Additionally, the results suggest that changes in extracellular enzyme activity and nutrient composition during SSF of H. erinaceus are closely associated with the mycelium growth stage, with a mutual promotion or inhibition relationship between the two. Our study offers a foundation for corn husk SDF fermentation and is relevant to the bioconversion of maize processing by-products.

Antioxidant capacity of fermented corn gluten meal in broiler chickens: a solid-state approach with mixed microbial fermentation

Fermentation of feed with probiotic and biofunctional properties has gained global attention for its potential to enhance digestive absorption and improve overall functional quality. This study investigates the antioxidant capacity and expression of antioxidant-related genes in broiler chickens fed with fermented corn gluten meal (FCGM) containing mixed microbial cultures. Seventy-two male Yellow-Feathered broiler chickens were randomly assigned to 2 groups, each consisting of 3 replicates, and were fed experimental diets containing either corn gluten meal or FCGM for 42 d. The antioxidant capacity of FCGM was assessed in vivo. Chickens fed with FCGM exhibited significant increases in serum glutathione concentration, as well as enhanced activities of total superoxide dismutase, glutathione peroxidase, and catalase (CAT) in their serum. Similar trends were observed in the liver, specifically in the activities of glutathione peroxidase and CAT. Additionally, the expression levels of key antioxidant-related genes in the liver, such as glutathione synthase, superoxide dismutase 1, superoxide dismutase 2, CAT, and glutathione peroxidase 1, were examined. The results indicated that FCGM significantly enhanced antioxidant capacity in broiler chickens. This study highlights the potential benefits of utilizing solid-state fermentation with mixed microbial cultures to improve the antioxidant properties of corn gluten meal, thereby contributing to the overall health and well-being of broiler chickens.

Dynamic changes in the metabolome and microbiome during Citrus depressa Hayata liquid fermentation

Citri Reticulatae Pericarpium (CRP) is a common traditional Chinese herbal medicine, valued for its multi-bioactivity. However, its processing time, environment, and microorganisms all affect its quality and bioactivity. To address this, the study replaced solid-state fermentation with liquid fermentation using microorganisms and isolated Bacillus amyloliquefaciens, respectively. This aimed to discover a more stable processing method and examine metabolite-micobiota correlations. Non-targeted metabolomics identified 70 differential metabolites, focusing on amino acids, polymethoxyflavones (PMFs), and carbohydrates. Long-read sequencing showed a shift in dominant bacterial genera from Lactobacillus to Pediococcus, then to Clostridium. Spearman analysis revealed a positive correlation between specific Clostridium species and PMFs production. B. amyloliquefaciens fermentation notably increased PMFs content without reducing hesperidin levels, suggesting its potential as an alternative processing method. This study offers valuable insights into metabolome-microbiome interactions for future biotransformation research.

Fungi species identified from polluted environment for chromium sequestration and solid state fermentation on tannery shaving waste

Accumulation of hexavalent chromium in the environment affects our ecosystem. Physico-chemical treatment did not solve the problem, due to high requirement of operational costs & energy, insolubility of Cr (VI) at any pH & sludge accumulation. The study aim is screening and evaluating fungi for chromium biosorption for mycoremediation. Soil and effluent sample were collected. PDA media was used for fungi purification. Fungal chromium tolerance evaluation and optimization was conducted at pH (4, 7, 10), T0 (25, 27.5, 35 °C), Cr concentration (5000–25000 ppm) using Full Factorial experimental design. Spore count, biomass production, Cr tolerance index, mycelia growth were evaluated. Flame Absorptive Spectrophotometer was used for quantification of fungal chromium removal. Fungi species were identified by MALDI-TOF. Fungi growth & degradation of tannery shaving waste was evaluated. The result revealed 6 potential fungi, T. longibrachiatum, T, koningii, A. niger, G. candidum, P. rubens, T. orientale were identified. Optimium mean biomass & spore count were 0.514 ± 0.051& 1.39 ± 0.038 at pH4 and 27.5 °C respectively. MTL test indicate that Trichoderma species, A. niger & P. rubens survive up to 10,000 ppm, 15, 000 ppm & 20,000 ppm respectively. FAAS analysis of fungi chromium removal from aqueous media result indicate that A. niger (99%). T. longibrachiatum (85%) and P. ruben (84.6%). These 6 fungi are efficient in tannery shaving waste degradation but A. niger was superior in spore count 15.1 Log/mL and 7 g substrate weight loss. In conclusion three fungi have high chromium tolerance and removal capacity and shaving waste degradation promising for mycoremediation.

Production of Cellulolytic Enzymes by Paecilomyces TP08 Using Grape Stalk and Wheat Bran as Substrates in Solid State Culture

Objective: The objective of this study is to investigate the use of grape stems and wheat bran as substrates in solid state fermentation, for the production of cellulolytic enzymes using the fungus Paecilomyces TP08 sp. Theoretical Framework: In grape production, driven by increased consumption and exports, by-products represent 30% of the total volume of grapes processed for wine, requiring efficient management to ensure sustainability. Method: The methodology adopted for this research involves solid-state cultivation, with a substrate made up of 50% grape stems and 50% wheat bran, with samples taken every 24 hours. Each sample taken went through a filtration process, followed by enzyme activity analysis using the DNS method. Results and Discussion: The results obtained showed that the cultivation with the association of wheat bran and grape stalks presented good total cellulase activity during the process, value of 0.846 U/g in 144h, followed by the activity of 0.663U/g observed in 24h. Research Implications: The practical and theoretical implications of this research are discussed, providing insights into how the results can be applied or influence practices in the field of industrial biotechnology. These implications could cover the food, textile and pharmaceutical industries. Originality/Value: This study contributes to the literature by associating grape stalks with wheat bran for the production of fungal enzymes. The relevance and value of this research are evidenced by the use of an innovative substrate (grape stalks) associated with a conventional substrate (wheat bran) for induction of the microorganism little used in the literature for enzyme production.

Developing endophytic Penicillium oxalicum as a source of lignocellulolytic enzymes for enhanced hydrolysis of biorefinery relevant pretreated rice straw.

Endophytic fungi, as plant symbionts, produce an elaborate array of enzymes for efficient disintegration of lignocellulosic biomass into constituent monomeric sugars, making them novel source of lignocellulolytic CAZymes with immense potential in future biorefineries. The present study reports lignocellulolytic enzymes production potential of an endophytic halotolerant Penicillium oxalicum strain isolated from Citrus limon, under submerged and solid-state fermentation (SmF & SSF, respectively), in the presence and absence of salt (1M NaCl). The comparative QTOF-LC/MS-based exoproteome analysis of the culture extracts unveiled differential expression of CAZymes, with the higher abundance of GH6 and GH7 family cellobiohydrolase in the presence of 1M salt. The strain improvement program, employing cyclic mutagenesis and diploidization, was utilized to develop hyper-cellulase producing mutant strains of P. oxalicum. The enzyme production of the developed strain (POx-M35) was further enhanced through statistical optimization of the culture conditions utilizing glucose mix disaccharides (GMDs) as an inducer. This optimization process resulted in the lignocellulolytic cocktail that contained high titers (U/mL) of endoglucanase (EG) (146.16), cellobiohydrolase (CBHI) (6.99), β-glucosidase (β-G) (26.21), xylanase (336.05) and FPase (2.02 U/mL), which were 5.47-, 5.54-, 8.55-, 4.96-, and 4.39-fold higher when compared to the enzyme titers obtained in wild HP1, respectively. Furthermore, the lignocellulolytic cocktails designed by blending secretome produced by mutant POx-M35 with xylanases (GH10 and GH11) derived from Malbranchea cinnamomea resulted in efficient hydrolysis of unwashed acid pretreated (UWAP) rice straw slurry and mild alkali deacetylated (MAD) rice straw. This study underscores the potential of bioprospecting novel fungus and developing an improved strain for optimized production and constitution of lignocellulolytic cocktails that can be an important determinant in advancing biomass conversion technologies.

Mining of thermophilic biosurfactant producers for solid-state fermentation

Solid-state fermentation (SSF) is an emerging technology for organic waste valorisation to marketable bio products. SSF scale-up is hindered by heat transfer problems that could be diminished operating under thermophilic conditions. Compost samples collected from food waste composting facility in a primary school in Barcelona and textile industry sample from Faisalabad Pakistan were subjected to isolation of thermophilic biosurfactant producing microorganisms. Altogether 43 isolates were screened through biosurfactant qualitative screening, but 18 isolates dominated with promising results which were further shortlisted under solid-state culture to select the five significant performers belonging to Bacillus sp., Aspergillus sp., and Streptomyces sp. The performance of the five isolates in SSF was assessed in time course studies in 0.5-L packed bed bioreactor using winterization oil cake (WOC), wheat bran and glucose as substrates combined with wheat straw as support material. All five isolates colonized the substrate well in SSF systems and exhibited considerable glucose consumption and adaptation within the SSF setup. The fermentation extracts indicated promising surface-active properties as observed by emulsification and oil displacement analysis. These findings provide an effective enrichment strategy for screening of thermophilic biosurfactant producers and can aid establishment of the scale up for the enhanced metabolite production.

Improving mannanase production in Bacillus subtilis for fibre hydrolysis during solid-state fermentation of palm kernel meal

The primary challenge in utilizing palm kernel meal (PKM, an agricultural by-product) as non-ruminant livestock feed is its high fibre content, predominantly in the form of mannan. Microbial fermentation offers an economically favourable alternative to enzyme supplementation for breaking down fibre in lignocellulosic biomass. In a recent study, our group isolated a B. subtilis strain F6 with a fast response time for mannanase production upon exposure to PKM. This work focuses on improving the mannanase production of the B. subtilis strain to achieve greater fibre hydrolysis of PKM without extending fermentation time. Mannanase GmuG, sourced from B. subtilis F6 and verified for its hydrolytic activity on PKM fibre, was homologously expressed using a replicative plasmid (pBE-S). Enzyme production was systematically improved by optimizing various regulatory elements, including the promoter, ribosome binding site, and signal peptide. Consequently, the neutral detergent fibre content of PKM was substantially reduced by 36.4 % in 22 h of solid-state fermentation using the engineered strain. Lastly, the highest mannanase-producing strain was examined for scaled-up fermentation. The impacts of fermentation on fibre and protein contents, as well as the surface morphology of PKM, were analysed. The outcomes of this study offer an efficient method for robust mannanase expression in B. subtilis and its potential application in the biotransformation of PKM and other mannan-rich bioresources for improved feed utilization.

Upgrading the Bioactive Potential of Hazelnut Oil Cake by Aspergillus oryzae under Solid-State Fermentation.

Hazelnut oil cake (HOC) has the potential to be bioactive component source. Therefore, HOC was processed with a solid-state fermentation (SSF) by Aspergillus oryzae with two steps optimization: Plackett-Burman and Box-Behnken design. The variables were the initial moisture content (X1: 30-50%), incubation temperature (X2: 26-37 °C), and time (X3: 3-5 days), and the response was total peptide content (TPC). The fermented HOC (FHOC) was darker with higher protein, oil, and ash but lower carbohydrate content than HOC. The FHOC had 6.1% more essential amino acid and benzaldehyde comprised 48.8% of determined volatile compounds. Fermentation provided 14 times higher TPC (462.37 mg tryptone/g) and higher phenolic content as 3.5, 48, and 7 times in aqueous, methanolic, and 80% aqueous methanolic extract in FHOC, respectively. FHOC showed higher antioxidant as ABTS+ (75.61 µmol Trolox/g), DPPH (14.09 µmol Trolox/g), and OH (265 mg ascorbic acid/g) radical scavenging, and α-glucosidase inhibition, whereas HOC had more angiotensin converting enzyme inhibition. HOC showed better water absorption while FHOC had better oil absorption activity. Both cakes had similar foaming and emulsifying activity; however, FHOC produced more stable foams and emulsions. SSF at lab-scale yielded more bioactive component with better functionality in FHOC.