Solid-state Fermentation Technology Research Articles

Preparation of Plant Growth Enhancing Bioformulation from Agricultural Wastes by Solid State Fermentation

Preparation of organic waste based bioformulation through solid state fermentation technology for application in the field offers an ecofriendly and viable alternative to sustainable food production. The present study deals with the potential of seven agrowastes as substrate carriers for the growth of indigenous strains of Pseudomonas fluorescens (Pf) and Bacillus subtilis (Bs) that stimulate plant growth. The cosubstrate (CS) with equal proportion of the seven agrowastes and both the bioinoculants (CSPfBs) proved as the best substrate carrier with highest population load of the bioinoculants at 45 days after storage (DAS). Thereafter the population declined steadily in all the bioformulations from 60 DAS to 90 DAS. However, CSPfBs gave the highest population load at 90 DAS. As individual substrate for both Pf and Bs, vermicompost performed best with a population load of 9.95 of Pf and 9.98 of Bs at 90 DAS. The bioformulations CSPfBs, VBs and VPf when applied in soil, gave the best yield in brinjal plants (Solanum melongena L. cv. Pusa Kranti) at 30 days after transplanting. Similar trends were also observed in the other yield parameters. The study indicates the scope of the prepared bioinoculant as a low cost eco friendly option for promotion of growth and yield of crops.

Extraction of Cellulases Produced through Solid-State Fermentation by Trichoderma reesei CCT-2768 Using Green Coconut Fibers Pretreated by Steam Explosion Combined with Alkali

The industrial processing of coconut to produce valuable foods, such as water and milk, generates large volumes of waste, especially the fruit shell. Despite this, material can be used in bioprocess applications, e.g., the production of enzymes, its recalcitrance hinders the cultivation of microorganisms, and low productivity is usually achieved. In this study, the production of cellulolytic enzymes through solid-state fermentation (SSF) and their extraction was investigated using the green coconut fiber pretreated by steam explosion, followed by alkali. The fungus Trichoderma reesei CCT-2768 was cultivated, using an experimental design, to study the effect of the water activity and the amount of biomass in the reactor. The combination of the pretreatment strategies yielded more porous biomass, with less hemicellulose (5.38%, compared to 10.15% of the raw biomass) and more cellulose (47.77% and 33.96% in the pretreated and raw biomasses, respectively). The water activity significantly affected the production of cellulases, with maximum activity yielded at the highest investigated value (0.995). Lastly, the extraction of the enzymes from the cultivation medium was studied, and a 9 g/L NaCl solution recovered the highest CMCase and FPase activities (5.19 and 1.19 U/g, respectively). This study provides an important contribution to the valorization of the coconut residue through (i) the application of the steam explosion technology to optimize the production of cellulases using the SSF technology and (ii) their extraction using different solvents.

Effect of Pleurotus eryngii mycelial fermentation on the composition and antioxidant properties of tartary buckwheat

In this study, we investigated the effect of solid-state fermentation of Pleurotus eryngii on the composition and antioxidant activity of Tartary buckwheat (TB). Firstly, the solid-state fermentation of P. eryngii mycelium with buckwheat was carried out, and the fermentation process was explored. The results of the extraction process and method selection experiments showed that the percolation extraction method was superior to the other two methods. The results of extraction rate, active components and antioxidant activity measurements before and after fermentation of TB extract showed that the extraction rate increased about 1.7 times after fermentation. Total flavonoids, rutin and triterpene contents were increased after fermentation compared to control. Meanwhile, LC-MS results showed an increase in the content of the most important substances in the fermented TB extract and the incorporation of new components, such as oleanolic acid, ursolic acid, amino acids, and D-chiral inositol. The fermented TB extract showed stronger antioxidant activity, while the protein and amino acid contents increased by 1.93-fold and 1.94-fold, respectively. This research was the first to use P. eryngii to ferment TB and prepared a lyophilized powder that could be used directly using vacuum freeze-drying technology. Not only the use of solid-state fermentation technology advantages of edible fungi to achieve value-added buckwheat, but also to broaden the scope of TB applications. This study will provide ideas and directions for the development and application of edible mushroom fermentation technology and TB.

Effects of Fermented Wheat Bran on Blood Biochemical Parameters and Carcass Characteristics of Broiler Birds

The experiment was conducted during 5th September 17th October, 2022 (42 Days) in the Department of Veterinary Microbiology and Immunology, College of Veterinary Sciences and Animal Husbandry, Central Agricultural University, Selesih, Aizawl, Mizoram, India to study the effect of feeding fermented wheat bran on blood biochemical parameter and carcass characteristics of broiler birds. Two hundred (200) numbers of day-old chicks were divided into five dietary groups with four replicates in each group. Each replicate contained 10 birds. Five dietary treatments: basal diet (Control); basal diet with Bacitracin methylene disalicylate (AGP) @ 0.5 g kg-1 of feed; basal diet with inclusion of 10% wheat bran; basal diet with inclusion of 10% fermented wheat bran; and basal diet with inclusion 15% fermented wheat bran. The feed and water were given at free choice to the birds. Fermented wheat bran was prepared by inoculating Lactobacillus fermentum using Solid-state fermentation technology. Blood biochemical parameters like total protein, albumin, globulin, triglyceride, cholesterol, LDL and HDL did not differ significantly among the experimental groups. However, the glucose level showed significantly higher (p<0.01) at 28th and 42nd days old birds, whereas HDL was significantly (p<0.05) higher at 42nd day in AGP, FWB-10 and FWB-15 group as compared to control and WB-10 group at old birds. Therefore, it was concluded that 15% fermented wheat bran can be incorporated in the diet of broiler chickens without any adverse affect.

Changes in vinegar quality and microbial dynamics during fermentation using a self-designed drum-type bioreactor.

The bioreactor based on solid-state fermentation technology has been developed for vinegar production, standardization of fermentation process and stabilization of vinegar quality. The microbial community diversity, and volatile compounds of six cultivars of vinegar samples fermented in a self-designed solid-state fermentation bioreactors were investigated using Illumina MiSeq platform and gas chromatography mass spectrometry (GC-MS) technology. The correlations between the richness and diversity of microbiota and volatile profiles, organic acids, as well as physicochemical indicators were explored by R software with the coplot package. The findings indicated that Acetobacter, norank-c-Cyanobacteria, and Weissella played key roles during fermentation process. Norank-f-Actinopolyporaceae, norank-c-Cyanobacteria, Pediococcus, and Microbacterium had significant correlations with the physicochemical characteristics. The most common bacterial species were associated with a citric acid content, whereas the least number of bacterial species correlated with malic acid content. Findings could be helpful for the bioreactor optimization, and thus reaching the level of pilot scale and industrialization.

Evaluation of coffee bean husk fermented by a combination of Aspergillus niger, Trichoderma harzianum, and Saccharomyces cerevisiae as animal feed

Abundant coffee bean husk acquires an alternative source of fiber for livestock feed, but a high level of the crude fiber of it became an obstacle. Solid-state fermentation technology using lignocellulolytic fungi is known to be able to improve the nutritional quality of feedstuff that have high fiber content. Its mechanism is through the degradation of the lignocellulose fraction and enhance protein content. This study aimed to determine the nutritional quality of fermented coffee bean husk with a combination of fungi and yeast. The fermentation method used a solid-state fermentation consisting of 7 different inoculums, namely: P0: Unfermented coffee bean husk, P1: Aspergillus niger, P2: Saccharomyces cerevisiae, P3: Trichoderma harzianum, P4: Aspergillus niger + S. Cereviciase, P5: Aspergillus niger + Trichoderma harzianum, P6: Saccharomyces cerevisiae + Trichoderma harzianum and P7: Aspergillus niger + Saccharomyces. Cereviciase + Trichoderma harzianum. The nutritional quality of the fermented coffee bean husk was determined by proximate analysis, lignocellulolytic fraction, and digestibility. The data obtained were analyzed by ANOVA and followed by Tukey's post hoc test. The crude fiber content of fermented coffee bean husk (P1-P7) was lower than unfermented (P0). There was no significant difference among treatments in crude fat and protein. Treatment P3 has the highest total digestibility nutrient (70) and the lower crude fiber (15.03). A combination of Aspergillus niger and Saccharomyces cerevisiae reduce lignin content by about (4,16%). In conclusion, the fermented coffee bean husk can be utilized as animal feedstuff with higher nutritional quality than unfermented.

Biotechnological Application of Saccharomyces cerevisiae and Lactobacillus delbrueckii sp. bulgaricus for Protein Enrichment of Fermented Unmalted and Malted Sorghum (Sorghum bicolor (L.) Moench).

This study evaluated changes in protein contents of malted and unmalted sorghum, and their formulated blends, after fermentation for 10 days at 25°C with mono and cocultures of Saccharomyces cerevisiae and Lactobacillus delbrueckii sp. bulgaricus. Fermentation of unmalted and malted sorghum and their formulated blends of 1 : 1 (w/w), 3 : 1 (w/w), and 1 : 3 (w/w) by S. cerevisiae and L. bulgaricus could increase their protein contents. Thus, there was an increase in protein content of fermented, malted sorghum by 68.40% for S. cerevisiae, 34.98% for L. bulgaricus, and 76.59% for cocultures of S. cerevisiae and L. bulgaricus; protein contents of fermented, unmalted sorghum also increased by 58.20, 39.36, and 55.00% for monoculture of S. cerevisiae, monoculture of L. bulgaricus, and coculture of S. cerevisiae and L. bulgaricus, respectively. S. cerevisiae was more effective in enriching protein content of the 1 : 3 (w/w) formulated blend of unmalted-malted sorghum by 77.59%; L. bulgaricus was more effective in enriching protein content of the 3 : 1 (w/w) unmalted-malted sorghum blend by 60.00%; coculture of S. cerevisiae and L. bulgaricus enriched the protein content of 3 : 1 (w/w) unmalted-malted sorghum substrate by 44.54%. Significant (p ≤ 0.05) increases in fat with corresponding decreases in carbohydrate and fibre contents were consistently recorded in malted and unmalted sorghum. In the formulated blends of sorghum, fat, carbohydrate, and fibre contents either increased or decreased erratically after fermentation. There were significantly (p ≤ 0.05) higher protein contents in malted sorghum, compared to unmalted sorghum. These findings show that solid-state microbial fermentation technology, using S. cerevisiae and L. bulgaricus, either as mono- or coculture, could effectively enrich the protein contents of unmalted and malted sorghum and their formulated blends. The implications of the findings for infant and adult nutrition are discussed, and future work to augment findings is suggested.

Optimization of solid-state fermentation technology and analysis of key aroma components of compound rice wine

Optimization of solid-state fermentation technology and analysis of key aroma components of compound rice wine

Feasibility Study on Bioethanol Production by One Phase Transition Separation Based on Advanced Solid-State Fermentation

To fulfill the consumption demand of low-cost fuel ethanol, an advanced process for feedstock fermentation and bioethanol extraction was required. This study proposed a process of combined continuous solid-state distillation and vapor permeation to extract ethanol from fermented sweet sorghum bagasse on the basis of advanced solid-state fermentation technology. Ethanol undergoes only one phase transition separation in the whole process, which drastically reduces energy consumption compared to the repeating phase transitions that occur in conventional bioethanol production. The mass balance and energy consumption of combining processes were simulated overall. A techno-economic evaluation was conducted on the flowsheet. Costs and profit of fuel ethanol produced by one phase transition separation bioethanol-producing technology were comprehensively calculated. The results of the present study show that the proposed process is an energy efficient and cost-effective alternative to conventional bioethanol production.

Metabolic profile of main organic acids and its regulatory mechanism in solid-state fermentation of Chinese cereal vinegar

Shanxi aged vinegar (SAV), a traditional Chinese cereal vinegar, is produced using solid-state fermentation (SSF) technology. Organic acids are the key flavor compounds of vinegar. However, the metabolic mechanism of organic acids during SSF process is still unclear. In this study, metatranscriptomics was used to explore the metabolic profile of main organic acids in SSF. The results show that carbon metabolism is the dominant pathway during fermentation, among which pyruvate metabolism, glycolysis and starch and sucrose metabolism associated with organic acids were the most abundant. The metabolic pathways of acetic acid and lactic acid shift from acetyl-P and pyruvate pathways at early and middle-early stages of fermentation to acetaldehyde and L-lactaldehyde pathways at later stages, respectively, and Lactobacillus and Acetobacter are the predominant microorganisms contributed to them. Temperature and acetic acid are proven to be the environmental factors that regulate the metabolic activity during SSF. This study sheds new lights on metabolism of flavor substances in the spontaneous ecosystems of traditional fermented food.

Microbial alkaline serine proteases: Production, properties and applications.

Proteolytic enzymes hold a pivotal position in numerous industrial processes where hydrolysis of protein molecules is required under precise conditions. The emerging trend of biotechnological applications in recent years has witnessed a renewed interest in alkaline serine proteases extending their utility in detergent, leather, textile, food and pharmaceutical industries. A variety of microorganisms have been reported to produce alkaline serine proteases on a large scale, however, extensive research to find an alkaline serine protease with desirable characteristics such as significant catalytic efficiency, expanded stability and broad substrate specificity is still ongoing. Although submerged fermentation dominates the commercial enzyme production, recent reports have emphasized on solid state fermentation technology which can reduce major cost associated with the enzyme production. In the present review, recent research on alkaline serine proteases along with their novel properties and production using solid state fermentation have been discussed.

Valorization of agro-industrial wastes by producing 2-phenylethanol via solid-state fermentation: Influence of substrate selection on the process

2-phenylethanol (2-PE) is a value-added compound widely used in industry due to its rose-like odor and antibacterial properties that can be bioproduced using wastes as raw materials. This study presents the valorization of nine agro-industrial wastes as potential substrates for 2-PE production using an isolated 2-PE producer Pichia kudriavzevii, and the solid-state fermentation (SSF) technology as an alternative approach. The assessed substrates comprised wastes of varied traits such that each of them provided different characteristics to the fermentation. Thus, by using a principal component analysis (PCA), it was possible to identify the most significant characteristics associated with the substrates affecting the 2-PE production. Results show that L-phenylalanine biotransformation was more efficient than de novo synthesis for producing 2-PE. Besides, from the evaluated set, the maximum 2-PE production was achieved with red apple pomace, reaching 1.7 and 25.2 mg2PE per gram of used waste through de novo and L-phenylalanine biotransformation, respectively. In that scenario, volumetric productivity and precursor yield were 39.6 mg2PE L-1h−1 and 0.69 g2PE per gram of L-phenylalanine added, respectively. From the PCA, it was identified that the reducing sugars content of the substrate, the air-filled porosity of the bed and the L-phenylalanine availability were the most critical parameters (associated with the substrates) influencing the microbial activity and 2-PE production. These results suggest that the desirable traits a solid media needs for promoting 2-PE production via SSF could be reached by using a combination of wastes in a synergistic approach.

Increasing nutrient quality and in vitro digestibility of mixed feed oil palm waste for ruminant feed by solid-state fermentation technology

Palm oil cake (BS) and Solid ex decanter (SD) are feed ingredients produced from palm oil processing which is available in large quantities. BS and SD have high protein content could be used as ruminant feed but have high fat content could be decreased rumen metabolism. Therefore. solid-state fermentation (SSF) technology is one way to overcome this problem. This study aims to improve the nutritional quality and digestibility of mixed feed palm oil cake and solid ex decanter (BS/SD) which is fermented by Rhizopus oligosporus (RO) mushroom. Application SSF technology for different combination of mixed feed BS/SD (70/30, 50/50 and 30/70) was carried out for 6 days which was then analyzed on the quality of the proximate. fiber fractions and in vitro true dry matter digestibility (IVTDMD) value (daisy incubator ANKOM Technology). The result showed that the mixed feed BS/SD 50/50 was the best combination with Rhizopus oligosporus inoculum with doses of 0.2, 0.4 and 0.8%. Hence, this SSF technology was effective process for increasing protein content and in vitro true dry matter digestibility (IVTDMD) 60% - 67.26% with combination BS/SD 50/50 and RO inoculum with doses 0.2 and 0.4 percent.

Longitudinal Assessment of the Tiger Milk Medicinal Mushroom, Lignosus rhinocerus (Agaricomycetes), Sclerotium Cultivar: Uniformity of Bioactive Components.

Traditional use of the tiger milk medicinal mushroom, Lignosus rhinocerus, to treat various illnesses has been recorded for > 4 centuries. Successful cultivation of L. rhinocerus using proprietary solid-state fermentation (SSF) technology by LiGNO Biotech has enabled large-scale production of L. rhinocerus sclerotia (termed L. rhinocerus TM02) and further investigations into its medicinal properties. Pharmacological activities of L. rhinocerus TM02, including its antioxidant, anti-inflammatory, anticancer, and immunomodulatory effects and the bioactive components responsible, have been validated by various scientific studies. In this study, we assessed the consistency of the bioactive components in 11 batches of L. rhinocerus TM02 produced over a 9-year period. The different batches of L. rhinocerus TM02 consisted of stable protein, polysaccharide, and glycoprotein contents, and all tested samples were comparable to the wild type. L. rhinocerus TM02 had greater protein, carbohydrate, and glycoprotein contents, which were mostly bioactive compared to another cultivar from a different cultivation technology (TM-UN). Together with previous scientific validations, L. rhinocerus TM02 produced using SSF cultivation is of optimal quality with high consistent bioactive contents, which can be an appropriate indicator for quality validation of the much sought-after medicinal mushroom, L. rhinocerus.

Solid-state fermentation technology and innovation for the production of agricultural and animal feed bioproducts

It has now passed more than forty years since solid-state fermentation (SSF) research developments have gained importance for the scientific community. After so many years, numerous processes and equipment for SSF were studied and designed focusing on the production of different commercially relevant bioproducts such as enzymes, fermented food, such as Chinese daqu and koji, organic acids, pigments, phenolic compounds, aromas, biosorbents and so many others. However, no review paper has been focused yet specifically on agricultural and animal feed bioproducts obtained through SSF techniques. This review comprises the description of agricultural sub-products that have been employed in most important developed processes concerning the production of animal feed products and agricultural products such as spores, probiotics, biofungicides, bioinsecticides and other biopesticides, biofertilizers and plant growth hormones. Major designed SSF bioreactors are also described and the most important related cases of successful employment of the technique are reported. Finally, a summary of patents and innovations regarding SSF products and processes in this area is presented, showing that the main involved countries are China, South Korea, India and the USA. It is clear that the interest in this theme is increasing and that scientific and technological developments are still needed.

Effective removal of Cr(VI) in aqueous solutions using Caulis lonicerae residue fermented by Phanerochaete chrysosporium

Cr(VI) is one of the most common environmental pollutants. The non-biodegradable Cr(VI) in aqueous solution accumulates along the food chain and damages the health of plant, animal, and human. In this study, solid-state fermentation technology was used to treat Caulis lonicerae residue to improve its adsorption capacity for Cr(VI). Caulis lonicerae can be used to extract the active ingredients such as organic acids, flavonoids, and triterpenoid saponins that have various effects including anti-oxidation and immune boosting. However, there is no proper treatment for large amount of residue left after extraction. The Phanerochaete chrysosporium was inoculated into the residue for solid-state fermentation, and the adsorption capacity of C. lonicerae residue before (CLr) and after fermentation (FCLr) regarding Cr(VI) adsorption was compared. In the range of 40–120 mg/L Cr(VI), the adsorption capacity of FCLr was significantly higher than that of CLr. The scanning electron microscopy (SEM) results exhibited a rougher surface of FCLr. The Fourier-transform infrared spectroscopy (FTIR) results revealed that the structure of FCLr was affected by the combination of Cr(VI), and the multiple functional groups interacted with Cr(VI) (such as –OH, C–H, C = O, C–O–C, and C–O). The adsorption capacity could reach 48.91 mg/g and the Cr(VI) removal percentage may reach 98.07% for FCLr increased by 28.24% through fermentation.

High-Protein Solid-State Symbiotic Fermentation of Sauce Residue for Probiotic Feed

The abuse of antibiotics in animal feed has caused a series of problems in livestock breeding, meat products and the natural environment. In this study, sauce residue was used as the main raw material that includes 25.98% of dry-based crude protein, 3.91% of NaCl, 16.28% of crude fat, 11.06% of the ash and the multi-strain solid-state symbiotic fermentation technology was used to increase the amount of probiotics and the crude protein content of feed. Meanwhile, the addition of functional probiotics improved the feed palatability, while reducing the use of antibiotics further improved the cycle utilization of soy sauce residue. This study systematically optimized the symbiotic conditions of two probiotics, Lactobacillus bulgaricus and Saccharomyces cerevisiae. This study defined viable cell count and crude protein content as the core targets for analysis and evaluation. Firstly, the optimal carbon source concentration, the temperature and the inoculation process of symbiotic fermentation were determined by single factors; then the symbiotic fermentation conditions (inoculation volume, material-liquid ratio, fermentation time) were optimized by orthogonal test. The results showed that 40 g/L glucose/lactose (50/50%) was the best carbon source for sauce residue fermentation. The optimum fermentation conditions were a ratio of material to water of 1:0.8 and an inoculation volume of 15% (v/w) and a fermentation duration of 48 h. Meanwhile, the study found that multi-step temperature control could effectively improve the corresponding targets. The inoculation with Saccharomyces cerevisiae first and then with Lactobacillus bulgaricus after 24 h, boosted the probiotic quantity and protein content. In optimized conditions, probiotic viable count reached 7.2×108 CFU·mL-1 and the crude protein content increased from 25.98% (dry content) to 38.86%, which is 49.6% increase compared with the raw material. This research could provide a reference for the development of high-protein probiotic feed using sauce residue.

Metabolism analysis for enhanced nutritional profile of chestnuts subjected to anerobic solid‐state fermentation by probiotic lactic acid bacteria

The improved nutritional composition of anaerobic solid-state fermentation (SSF) with broken dried chestnut by probiotic lactic acid bacteria (LAB), namely Lactobacillus casei strain CU (CU) and Lactobacillus fermentum strain KF5 (KF5) was evaluated. Preliminary sensory evaluation results showed that fermented chestnut had unique flavor characteristics between perception of sour and of chestnut. The number of LABs in fermented chestnut samples was not less than 8 log10 cfu/g under the condition of 40 days storage at 4°C. Chestnut fermented with KF5 had a slightly better antioxidant activity to reduce the 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical of 87% than the unfermented control (70.12%). Significant increases of 10.53% and 21.16% in protein digestibility of samples were observed following SSF with CU and KF5, respectively. The extracts of the fermented chestnut showed a less intense band just below 25 kDa in the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The gas chromatography-mass spectrometer (GC-MS) extracellular metabolite analysis showed that the complex macromolecules in chestnut was degraded into simple sugars, organic acids, amino acids, and fatty acids. The findings of the study provide the possibility of using fermented chestnuts as potential healthy functional food. Practical applications At present, the application scope of modern chestnut preservation technology is not very wide, which is limited by cost and other factors. Therefore, the development of in-depth processing technologies of chestnut is one of the important ways to have a positive influence on the chestnut market. Nowadays, people focus on functional foods that can give full play to the body's defensive function, regulate physiological rhythm, prevent diseases, and promote rehabilitation, rather than just satisfying appetite or nutrition. Consumer attention to consume probiotic foods contributing to the maintenance of a good state of health through their biologically active ingredients has been significantly increased. This topic combines the characteristic resources of chestnut with selected probiotic lactic acid bacteria (LAB) through food biotechnology and uses anaerobic solid-state fermentation (SSF) technology to develop healthy functional food with high nutritional value and in line with people's consumption concept: chestnut products with good nutritional flavor and probiotic functional, which further improves the nutritional value of products.

Challenges of Enzymes, Conidia and 6-Pentyl-alpha-pyrone Production from Solid-State-Fermentation of Agroindustrial Wastes Using Experimental Design and T. asperellum Strains

In a context of growing awareness regarding environmental protection, biomass valorization is gaining a lot of attention. The byproducts volumes generated by agro-industry are massive and, left to decay, can constitute environmental pollutions. Use of agro-industrial wastes and solid-state fermentation (SSF) technology offers advantages to produce value-added products such as antibiotics, pigments, aromas and enzymes of industrial interest like cellulases, chitinases, amylases, etc. Several studies have already demonstrated the advantages of SSF for the production of fungal metabolites, yet the optimal conditions for metabolites production strongly depend on the culture conditions and microbial strain utilized. Therefore, the aim of this study was to improve the conidia, lytic enzymes (cellulase, lipase and amylase), and antifungal—6-pentyl-alpha-pyrones (6-PP)—production by three Trichoderma asperellum strains cultivated using SSF. Designs of experiments have been achieved in order to identify influential factors on 6-PP, conidia and enzymes (cellulase, lipase, and amylase) production by the fungal culture. A significantly enzymes activities, conidiation and 6-PP production were observed on mix of substrates: vine shoots, potatoes flour, jatropha, olive pomace and olive oil on high carbon/nitrogen ratio 37 which was used by T. asperellum TV104 as a source of nutrients and also as a matrix.

Establishment and verification of a model for the movement of pulverized sweet sorghum stalks in a rotary drum bioreactor by discrete element method

The mixing of raw materials in a rotary drum bioreactor is important for advanced solid-state fermentation technology. However, the shape, size, and other properties of pulverized sweet sorghum stalk particles are more complicated than those of the spherical particles. In this study, a soft rod-shaped discrete particle model was established and verified to simulate the mixing behavior of sweet sorghum stalk particles in a rotary drum bioreactor. We were inspired by the particle shape and established a rod-shaped particle model by investigating the influence of the shape (length–diameter ratio) and size (diameter) on the particle packing (stack height and bed porosity). We used orthogonal simulations and extremum difference analysis to determine the main factors, optimum level, and groups of other parameters. Based on calibrated parameters, twelve sets of simulations of radial mixing in the drum were performed, and the results were compared with experiments conducted under identical operating conditions. The average relative error between the simulation and the experiment was 10.95%, which indicates that they agreed well and that the simulation could predict the mixing process well.