Effect of particle size and ammonium sulfate concentration on rice bran fermentation with the fungus Rhizopus oryzae

Valorization of agro-industrial waste through solid-state fermentation: Mini review

Agriculture and industrial waste are produced in large volumes every year worldwide, causing serious concerns about their disposal. These wastes have high organic content, which microorganisms can easily assimilate into relevant value-added products. Valorization of agro-industrial waste is required for sustainable development. Solid state fermentation is an excellent method of utilizing waste for circular bioeconomy. Exploitation of agro-industrial waste as a substrate utilizing microorganisms for solid state fermentation provides beneficial products for use in industries and other fields. The use of waste reduces the cost of production of value-added products. This method is an environmentally friendly, economical and feasible approach for waste management. This review discusses the factors affecting the production of value-added products through solid state fermentation. It also discusses the valuable products from solid state fermentation technology, such as antibiotics, enzymes, organic acids, bioremediation, biosurfactants and biofertilizers. Challenges and future prospects are also presented.

Production of fermented milk analogs using subcritical water extraction of rice by-products and investigation of its physicochemical, microbial, rheological, and sensory properties

Rice milling by-products extract and Persian grape syrup (Persian grape molasses), as the proper alternatives for milk ingredients and sucrose, respectively, can be considered a promising way to produce functional milk analogs. In this study, we studied the production of rice milling by-product extracts via the subcritical water extraction method, as a green method. The optimum extract was then fermented by Lactobacillus casei and Lactobacillus plantarum, and the different physicochemical, sensory, and rheological properties and the viability of these lactic acid bacteria were assessed during fermentation and certain intervals of 28-day storage. Considering rheological properties, the optimum rice milling by-product extract was recognized based on DOE analysis and the rheological curves of fermented drinks and Persian grape molasses were fitted by Herschel-Bulkley and Bingham models, respectively. The extract and also milk analog had excellent fitness with Herschel-Bulkley model, and this fermented milk analog showed a drop in the consistency index, flow behavior, and yield stress during the 28-day storage. According to the results, the viable cell count of Lactobacillus plantarum and Lactobacillus casei remained at 106-108 colony forming unit/mL after 28-day storage, which showed a combination of rice milling by-product ingredients and inulin had a positive effect on the survival rate of lactic acid bacteria. An increase in values of total phenolic compounds, as well as antioxidant activity observed during fermentation; however, these compounds dropped considerably during storage as a result of degradation and interaction with other compounds. Moreover, in terms of sensory evaluation, Lactobacillus plantarum drinks provided the highest overall acceptability among other samples on the 28th day.

Enrichment of Fruit Peels' Nutritional Value by Solid-State Fermentation with Aspergillus ibericus and Rhizopus oryzae

The fruit processing industry is responsible for disposing of huge amounts of byproducts, especially fruit peels (FPs), which are often discarded in landfills. Using FPs in biotechnological processes contributes to a circular economy, reducing the environmental burden of FPs and increasing the revenue of the fruit processing industry. This study was focused on upgrading the nutritional value of orange (OPs) and banana (BPs) peels by solid-state fermentation (SSF) with filamentous fungi. SSF factors (moisture, fermentation time, inoculum size, ammonium sulfate (AS), and corn steep liquor (CSL)) and fungi species (Aspergillus ibericus and Rhizopus oryzae) were studied by a variable screening Plackett-Burman design. Both fungi grew on untreated FPs, increasing their protein content and antioxidant activity. Moisture, AS, and CSL were further studied by a Box-Behnken design with A. ibericus. Fermented OPs at 70% moisture and 0.005 g/g AS increased their protein content by 200%, whereas BPs at 70% moisture and 0.005 g/g CSL increased by 123%. Fermented peels were enriched in protein, fiber, and minerals, with a low content of carbohydrates and soluble sugars. Fermented OPs and BPs showed higher antioxidant activity than unfermented peels. The SSF of these FPs is an innovative approach that contributes to obtaining rich nutrient-fermented peels for food.

Lipolytic production from solid-state fermentation of the filamentous fungus Penicillium polonicum and its applicability as biocatalyst in the synthesis of ethyl oleate

Lipases represent versatile biocatalysts extensively employed in transesterification reactions for ester production. Ethyl oleate holds significance in biodiesel production, serving as a sustainable alternative to petroleum-derived diesel. In this study, our goal was to prospect lipase and assess its efficacy as a biocatalyst for ethyl oleate synthesis. For quantitative analysis, a base medium supplemented with Rhodamine B, olive oil, and Tween 80 was used. Solid-state fermentation utilized crambe seeds of varying particle sizes and humidity levels as substrates. In the synthesis of ethyl oleate, molar ratios of 1:3, 1:6, and 1:9, along with a total enzymatic activity of 60 U in n-heptane, were utilized at temperatures of 30 °C, 37 °C, and 44 °C. Reactions were conducted in a shaker at 200 rpm for 60 min. As a result, we first identified Penicillium polonicum and employed the method of solid-state fermentation using crambe seeds as a substrate to produce lipase. Our findings revealed heightened lipolytic activity (22.5 Ug-1) after 96 h of fermentation using crambe cake as the substrate. Optimal results were achieved with crambe seeds at a granulometry of 0.6 mm and a fermentation medium humidity of 60%. Additionally, electron microscopy suggested the immobilization of lipase in the substrate, enabling enzyme reuse for up to 4 cycles with 100% enzymatic activity. Subsequently, we conducted applicability tests of biocatalysts for ethyl oleate synthesis, optimizing parameters such as the acid/alcohol molar ratio, temperature, and reaction time. We attained 100% conversion within 30 min at 37 °C, and our results indicated that the molar ratio proportion did not significantly influence the outcome. These findings provide a methodological alternative for the utilization of biocatalysts in ethyl oleate synthesis.

Solid-state fermentation in an earthen vessel: Trichoderma viride spore-based biopesticide production using corn cobs

The present study reports the production of Trichoderma viride spores in an earthen vessel using corn cobs. Using 4 kg of corn cobs, spore-based biopesticide was produced after 21 d with a maximum spore count of 2.50 × 109 spores/g of substrate and a moisture reduction from 70.80% w/v to 8.10% w/v. The gas chromatography-mass spectrometry analysis of its ethyl acetate extract revealed that it had 20 secondary metabolites, of which 13 were known to be antimicrobial, one was plant growth-promoting, and one performed both functions. Dried extract dissolved in methanol showed the minimum fungicidal concentration of 5-10 mg/ml against Rhizoctonia solani on potato dextrose agar plate. Plate assays and pot experiments on Rhizoctonia solani-infected potato plants exhibited good antifungal and plant growth-promoting activities. The biopesticide showed 71.28% viability over 10 m of storage in the same earthen vessel at 30 ± 2 °C. Thus, a simple, robust technology was developed with good potential for farm deployment.

Effect of Rhizopus oryzae fermentation on proximate composition, anti-nutrient contents, and functional properties of banana peel flour

The present work aimed to evaluate the effect of fermentation by Rhizopus oryzae on the proximate composition, anti-nutrient contents, and functional properties of banana peel flour using the solid-state fermentation method in a tray bioreactor at 30°C for 96 h. Throughout fermentation, samples were obtained at different times (0/NF, 24, 48, 72, and 96 h), and analysed using standard procedures to determine the proximate composition, anti-nutrient contents, and functional properties. Based on the results, there were significant differences observed (p < 0.05). Carbohydrate content decreased by 3.35%, while the crude protein, fat, ash, and crude fibre contents increased by 11.12, 2.43, 10.99, and 3.50%, respectively. Hydrogen cyanide, saponin, oxalate, and phytate contents decreased by 42.59, 25, 23.83, and 43.82%, respectively. Water absorption capacity (WAC) and the water solubility index (WSI) increased by 3.94 and 37.14%, respectively, while oil absorption capacity (OAC) decreased by 4.48%. These results showed that the fermentation of banana peel flour by R. oryzae has potential benefits for the food industry due to its effect on chemical composition and functional properties.

Transcalar Design: An Approach to Biodesign in the Built Environment

Biodesign holds the potential for radically increasing the sustainability of the built environment and our material culture but comes with new challenges. One of these is the bridging of the vast differences of scale between microbiological processes and architecture. We propose that a transcalar design approach, which weaves together nonlinear dependencies using computational design tools and design methodologies through the biological generation of architectural components, is a way towards successful design implementations. Such design processes were explored in a laboratory-based fabrication and study of a column element. This column, named Protomycokion, serves to illustrate how design methodologies, particularly through the use of a demonstrator artefact, can serve to navigate the multiple scales, disciplines, and experiments that are necessary to engage the complexities of biodesign. Transcalar design processes embrace the adaptability, variability and interdependence of biological organisms and show possible gains with regard to material sustainability and increased performativity.

Investigation on mycelial growth requirements of Cantharellus cibarius under laboratory conditions

The golden chanterelle represents one of the commonly found, edible mushrooms that is highly valued in various cuisines. The present study focused on assessing the requirements of Cantharellus cibarius such as pH, temperature, as well as the carbon and nitrogen sources for mycelial growth. Optimization of the growth parameters was carried out by one-factor-at-a-time method. The optimal pH and temperature were determined to be 6.0 and 22.5 °C, respectively. Among the various carbon sources studied, sucrose at a concentration of 2% gave maximum mycelial growth and proved to be the most suitable one. Amongst the nitrogen sources studied, peptone, ammonium sulphate, and sodium nitrate, gave the maximum mycelial growth at an optimized concentration of 0.5%. In the presence of beef extract and yeast extract, a change in colony pigmentation from yellow to dark grey was observed. Finally, the carbon to nitrogen ratio of 2:0.5 proved to be optimal for mycelial growth. This study is the first report on the optimisation of in vitro growth requirements of C. cibarius.

Aspergillus oryzae Fermented Rice Bran: A Byproduct with Enhanced Bioactive Compounds and Antioxidant Potential

Rice bran (RB) is a byproduct of the rice industry (milling). For the fermentation process and to add value to it, RB was sprayed with fungal spores (Aspergillus oryzae MTCC 3107). The impact of fermentation duration on antioxidant properties was studied. Total phenolic content (TPC) determined using the Folin–Ciocalteu method, increased during fermentation until the 4th day. The antioxidant activity analyzed using the 2,2 Diphenyl–1′ picrylhydrazyl (DPPH) assay, total antioxidant activity (TAC), 2,2′-azinobis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS⁺) assay, reducing power assay (RPA) and hydroxyl free radical scavenging activity (HFRSA) for fermented rice bran (FRB) were determined and compared to unfermented rice bran (URB). TAC, DPPH, ABTS⁺ and RPA of FRB increased till 4th day of fermentation, and then decreased. The specific bioactive constituents in extracts (Ethanol 50%) from FRB and URB were identified using high performance liquid chromatography (HPLC). HPLC confirmed a significant (p < 0.05) increase in gallic acid and ascorbic acid. On the 4th day of fermentation, the concentrations of gallic acid and ascorbic acid were 23.3 and 12.7 µg/g, respectively. The outcome of present investigation confirms that antioxidant potential and TPC of rice bran may be augmented using SSF.

The Quality of Ciders Depends on the Must Supplementation with Mineral Salts

Providing yeast with the right amount of mineral salts before fermentation can contribute to improving the entire technological process, resulting in a better-quality final product. The aim of this study was to assess the impact of apple must supplementation with mineral salts ((NH4)2SO4, MgSO4, (NH4)3PO4)) on enological parameters, antioxidant activity, total polyphenol content, and the profile of volatile cider compounds fermented with various yeast strains. Rubin cultivar must was inoculated with wine, cider, and distillery or wild yeast strains. Various mineral salts and their mixtures were introduced into the must in doses from 0.167 g/L to 0.5 g/L. The control sample consisted of ciders with no added mineral salts. The basic enological parameters, antioxidant properties, total polyphenol content, and their profile, as well as the composition of volatile compounds, were assessed in ciders. Must supplementation with magnesium salts significantly influenced the use of the analyzed element by yeast cells and was dependent on the yeast strain. In supplemented samples, a decrease in alcohol concentration and total acidity, as well as an increase in the content of extract and total polyphenols, was observed compared to the controls. The addition of ammonium salts caused a decrease in the amount of higher alcohols and magnesium salts, as well as a decrease in the concentration of some esters in ciders.

Particle size reduction of rice straw enhances methane production under anaerobic digestion

The objective of this study was to investigate the effects of particle size reduction (20, 1, 0.15, and 0.075 mm) on biogas production from rice straw waste through batch anaerobic digestion experiments. To clarify the digestion mechanisms, the microbial community and rice straw properties including fractal dimension, dissolution abilities and the bio-liquefaction degree were determined. Particle size reduction of rice straw improved methane yield from 107 mL g^-1 VS to 197 mL g^-1 VS. The elevated digestion efficiency was attributed to the cellulose degradation (degradation rate from 27% to 93%) rather than hemicellulose or lignin. The comminution pretreatment improved the basic morphology, dissolution abilities and bio-liquefaction degree, which associated with the shifts in the bacterial community and the decreased bacterial diversity. These results suggested that particle size reduction of the rice straw in conjunction with optimized microbial growth could improve the methane yield in anaerobic digestion processes.

Solid-State Yeast Fermented Wheat and Oat Bran as A Route for Delivery of Antioxidants

The purpose of our study was to evaluate the potential of solid-state yeast fermentation (SSYF) in improving the phenolic acid content and composition, and the antioxidant activity of commercial wheat bran (WB) and oat bran (OB). The ultrasound-assisted methanolic extracts were compared for their total phenolic content (TPC), phenolics composition, and in vitro antioxidant activity in order to study the effect of fermentation time on the chemical profile and activity of bioactive compounds. The comparative analysis revealed significant differences (p < 0.05) between days of fermentation (0 through 6). The highest TPCs were obtained on day 3 for WB (0.84 ± 0.05 mg of gallic acid equivalents [GAE]/g dry weight [DW]), and on day 4 for OB (0.45 ± 0.02 mg GAE/g DW). The highest relative percentage increase in the phenolics concentration of WB was also registered on day 3 (ferulic acid +56.6%, vanillic acid +259.3%, dihydroxybenzoic acids +161.2%, apigenin-glucoside +15.3%); for OB, this was observed on day 4 (avenanthramide 2f +48.5%, ferulic acid +21.2%). Enhanced antioxidant activities were significantly correlated with the highest TPCs. Our results suggest that SSYF may be a useful procedure for enrichment of antioxidants in cereal bran, considering the design of different functional foods and nutraceuticals.

Fermentation Biotechnology Applied to Cereal Industry By-Products: Nutritional and Functional Insights

Cereals are one of the major food sources in human diet and a large quantity of by-products is generated throughout their processing chain. These by-products mostly consist of the germ and outer layers (bran), deriving from dry and wet milling of grains, brewers' spent grain originating from brewing industry, or others originating during bread-making and starch production. Cereal industry by-products are rich in nutrients, but still they end up as feed, fuel, substrates for biorefinery, or waste. The above uses, however, only provide a partial recycle. Although cereal processing industry side streams can potentially provide essential compounds for the diet, their use in food production is limited by their challenging technological properties. For this reason, the development of innovative biotechnologies is essential to upgrade these by-products, potentially leading to the design of novel and commercially competitive functional foods. Fermentation has been proven as a very feasible option to enhance the technological, sensory, and especially nutritional and functional features of the cereal industry by-products. Through the increase of minerals, phenolics and vitamins bioavailability, proteins digestibility, and the degradation of antinutritional compounds as phytic acid, fermentation can lead to improved nutritional quality of the matrix. In some cases, more compelling benefits have been discovered, such as the synthesis of bioactive compounds acting as antimicrobial, antitumoral, antioxidant agents. When used for baked-goods manufacturing, fermented cereal by-products have enhanced their nutritional profile. The key factor of a successful use of cereal by-products in food applications is the use of a proper bioprocessing technology, including fermentation with selected starters. In the journey toward a more efficient food chain, biotechnological approaches for the valorization of agricultural side streams can be considered a very valuable help.

Effect of the taxonomic group of fungi and type of substrate on the antioxidant activity of a solid-state fermentation system

The enzymatic and non-enzymatic antioxidant activities of a solid-state fermentation system (SSFS) employing six basidiomycete and four ascomycete fungi on orange peel have been evaluated. Class comparisons revealed highly significant effect of fungal group on the antioxidant activity. Peroxidase activity appeared only in the basidiomycete fungi (particularly Pleurotus columbinus, Ganoderma resinaceum, and Pleurotus floridanus) whereas catalase activity appeared in the two fungal groups in favor of the ascomycetes (particularly Paecilomyces variotii and Aspergillus fumigatus). Maximal peroxidase and minimal catalase activities were found at moderate phenolic content, with extreme phenolic levels leading to low peroxidase activity but high catalase activity. Production of the non-enzymatic antioxidants (phenolics, flavonoids, reducing power, and DPPH scavenging) was in favor of the ascomycetes, which showed great native ability to synthesize flavonoids and also to release flavonoids from orange peel. The basidiomycete fungi, which have limited native ability to produce phenolics, had high ability to consume orange peel phenolics. By contrast, the ascomycete fungi exhibited great native ability for production of phenolics and low ability to consume exogenous phenolics.

Fermentation: A Boon for Production of Bioactive Compounds by Processing of Food Industries Wastes (By-Products)

A large number of by-products or wastes are produced worldwide through various food industries. These wastes cause a serious disposable problem with the environment. So, now a day's different approaches are used for alternative use of these wastes because these by-products are an excellent source of various bioactive components such as polyphenols, flavonoids, caffeine, carotenoids, creatine, and polysaccharides etc. which are beneficial for human health. Furthermore, the composition of these wastes depends on the source or type of waste. Approximately half of the waste is lignocellulosic in nature produced from food processing industries. The dissimilar types of waste produced by food industries can be fortified by various processes. Fermentation is one of the oldest approaches and there are three types of fermentation processes that are carried out such as solid state, submerged and liquid fermentation used for product transformation into value added products through microorganisms. Selections of the fermentation process are product specific. Moreover, various studies were performed to obtain or fortified different bioactive compounds that are present in food industries by-products or wastes. Therefore, the current review article discussed various sources, composition and nutritive value (especially bioactive compounds) of these wastes and their management or augmentation of value-added products through fermentation.

Enhanced production of α-amylase by Penicillium chrysogenum in liquid culture by modifying the process parameters

In this paper, we have assessed the role of changing physicochemical parameters and substrate types on the production of α-amylase enzyme from Penicillium chrysogenum, with a view to determining the optimal conditions required for its maximum production. The findings of this research revealed that, at pH 6 using linseed oil cake as substratum, α-amylase enzyme production was maximum (550.0 U/mL), when the fungi was incubated for 6 days at 30 °C in 0.1 M acetate buffer. Further, reasonably good production of the α-amylase enzyme was also observed at pH 9 with all the experimented carbon sources as substrates. Moreover, statistical analysis, using analysis of variance (ANOVA) carried out to study the impact of different studied parameters on the α-amylase enzyme production revealed that incubation period of 6-18 days is highly significant (p = 0.01) factor in amylotic activity of the P. chrysogenum. Under the researched out optimal conditions, P. chrysogenum is an economically viable option for the industrial and biotechnological production of α-amylase enzyme.