Role of fungi in cyanogens removal during solid substrate fermentation of cassava

Summary Disinfected cassava root pieces were incubated with and without fungal inoculation. The resulting flours from non-inoculated incubated cassava showed significantly lower (P=0.004) cyanogenic glucoside levels than those from non-incubated cassava, and significantly higher (P < 0.0001) levels than those from the fermented pieces. The fungi played a role in the reduction of the cyanogenic glucoside levels.     

Effect of operating conditions on solid substrate fermentation

In this work the effects of environmental parameters on the performance of solid substrate fermentation (SSF) for protein production are studied. These parameters are (i) air flow rate, (ii) inlet air relative humidity, (iii) inlet air temperature, and (iv) the heat transfer coefficient between the outer wall of the fermentor and the air in the incubator. The air flow is supplied to effect cooling of the fermented mass by evaporation of water. A dynamic model is developed, which permits estimation of biomass content, total dry matter, moisture content, and temperature of the fermented matter. The model includes the effects of temperature and moisture content on both the maximum specific growth rate and the maximum attainable biomass content. The results of the simulation are compared with actual experimental data and show good agreement with them. The most important conclusions are that (i) the evaporative cooling of the biomass is very effective for temperature control and (ii) the air flow rate and the heat transfer coefficient have strong effects but they affect the biomass morphology and are not controllable easily. Also, a simple technique for the determination of the optimum temperature and moisture content profile for cell protein production is applied. The simulated biomass production increases considerably employing the optimum temperature and moisture content profiles. The ultimate goal is to implement the determined effects of the environmental parameters on the SSF biomass production and the temperature and moisture variation profiles to effectively control the SSF and optimize the biomass production. (c) 1993 John Wiley & Sons, Inc.     

Culture-independent analysis for determination of yeast diversity during solid substrate fermentation of grated cassava for gari production

Yeast diversity during fermentation of grated cassava for gari production in Nigeria was studied using culture independent methods based on Eukarya18S rDNA and the PCR-Denaturing Gradient Gel Electrophoresis (PCR-DGGE). DNA extracted directly from the grated cassava at different fermentation time regimes, as well as bulk cells generated from different viable count agar plates were used as template for amplification of 18S rDNA gene in a PCR experiment. Analysis of the 18S rDNA gene by sequencing of the PCR-DGGE band fragments revealed closest relative of Issatchenkia scutulata, Candida rugopelliculosa, Candida maritime, Zygosaccharomyces rouxii and Galactomyces geotricum as member of yeast community involved with the fermentation. PCR-DGGE can be useful for yeast in situ profiling during fermentation; this will contribute to safety of traditional fermented foods and optimization during large scale production of gari.     

Production of bacterial exopolysaccharides by solid substrate fermentation

In a comparison of submerged cultivation (SC) with solid substrate fermentation (SSF) for the production of bacterial exopolysaccharides (EPS), the latter technique yielded 2 to 4.7 times more polymer than the former, on the laboratory scale. SSF was performed using inert solid particles (spent malt grains) impregnated with a liquid medium. The polymer yields obtained from SSFs, as referred to the impregnating liquid volumes, were as follows: 38.8 g/litre xanthan from Xanthomonas campestris, 21.8 g/litre succinoglycan from Rhizobium hedysari and 20.3 g/litre succinoglycan from Agrobacterium tumefaciens PT45. These results make this technique promising for a potential application on the industrial scale. A further advantage with this fermentation process is found in the availability and low cost of substrates, which are obtained as by-products or wastes from the agriculture or food industry.     

Optimization of phytase production by solid substrate fermentation

The production of phytase by three feed-grade filamentous fungi (Aspergillus ficuum NRRL 3135, Mucor racemosus NRRL 1994 and Rhizopus oligosporus NRRL 5905) on four commonly used natural feed ingredients (canola meal, cracked corn, soybean meal, wheat bran) was studied in solid substrate fermentation (SSF). A. ficuum NRRL 3135 had the highest yield [15 IU phytase activity/g dry matter (DM)] on wheat bran. By optimizing the supplementation of wheat bran with starch and (NH₄)₂SO₄, phytase production increased to 25 IU/g DM. Optimization was carried out by Plackett-Burman and central composite experimental designs. Using optimized medium, phytase, phosphatase, alpha-amylase and xylanase production by A. ficuum NRRL 3135 was studied in Erlenmeyer flask and tray SSF. By scaling up SSF from flasks to stationary trays, activities of 20 IU phytase activity/g DM were reproducibly obtained. Electronic Publication     

Saccharification of cassava peels waste for microbial protein enrichment

Cassava waste peels may constitute up to 55% of the original tuber. These waste peels were found to contain 41.8% carbohydrate, 1.1% protein, 12.5% ether extract and 4.9%, 4.9% total ash. and 20.8% crude fibre. Studies were conducted to formulate a fermentation medium to convert the waste peels to reducing sugars and to enrich the peels with microbial protein. Amylase producing microorganisms were isolated from rotten cassava tuber discs buried in the soil at different locations. The microorganisms isolated were Aspergillus fumigatus, A. flavus, A. niger, and a Pseudomonas sp. and A. niger; the level of reducing sugar was 20.5 mg/ml. The lowest was by B. subtilis an isolate from fermenting locust bean. Generally the levels of saccharification were higher when the waste media were supplemented with different nitrogen sourses. The crude protein yield in the cassava peel waste media by different microorganisms varied from 5.6% to 17.5%. The highest protein yield was in the waste medium fermented by A. fumigatus followed by A. niger, B. subtilis, Pseudomonas sp. in decreasing order.     

Breeding and growth of Rhizopus in raw cassava by solid state fermentation

Nineteen Rhizopus strains were selected and tested for their growth capacity on raw cassava starch and their ability to produce amylase when grown on solid-state fermentations. Only three strains grew significantly on this natural substrate. Glucoamylase production was higher on raw cassava than on cooked cassava. After 48 h of fermentation, the protein content of cassava was increased from 1.75% to 11.3%. The byproducts of fermentation were fumaric acid, lactid acid and ethanol.     

Chitinase production by Beauveria felinaRD 101: optimization of parameters under solid substrate fermentation conditions

Major parameters affecting the production of chitinase by Beauveria felinaRD 101 under solid substrate fermentation conditions have been optimized. Wheat bran moistened with 100 MS-HCl medium adjusted to pH 5.0, inoculated with 1 × 10¹⁰ conidia g^–1 initial dry bran and incubated at 28 °C for 6 days produced maximum chitinase activity of 6.34 U g^–1 initial dry substrate.     

Bioconversion of lignocellulose in solid substrate fermentation

In this review the state of the art of lignocellulose bioconversion by solid substrate fermentation (SSF) is presented. The most important lignocellulolytic fungi and their properties are described, and their application in novel solid state bioreactors with on-line process control is discussed. The most important bioconversion products, biofuels, enzymes, animal feeds, biofertilizers, biopesticides, biopromoters, secondary metabolites, and the economy of their production by SSF is discussed. The use of SSF in the pulp and paper industry and in integrated crop management is illustrated.     

Heat transfer simulation in solid substrate fermentation

A mathematical model was developed and tested to simulate the generation and transfer of heat in solid substrate fermentation (SSF). The experimental studies were realized in a 1-L static bioreactor packed with cassava wet meal and inoculated with Aspergillus niger. A simplified pseudohomogeneous monodimensional dynamic model was used for the energy balance. Kinetic equations taking into account biomass formation (logistic), sugar consumption (with maintenance), and carbon dioxide formation were used. Model verification was achieved by comparison of calculated and experimental temperatures. Heat transfer was evaluated by the estimation of Biot and Peclet heat dimensionless numbers 5-10 and 2550-2750, respectively. It was shown that conduction through the fermentation fixed bed was the main heat transfer resistance. This model intends to reach a better understanding of transport phenomena in SSF, a fact which could be used to evaluate various alternatives for temperature control of SSF, i.e., changing air flow rates and increasing water content. Dimensionless numbers could be used as scale-up criteria of large fermentors, since in those ratios are described the operating conditions, geometry, and size of the bioreactor. It could lead to improved solid reactor systems. The model can be used as a basis for automatic control of SSF for the production of valuable metabolites in static fermentors.     

Sporulation of Penicillium roqueforti in solid substrate fermentation

Summary A study of the influence of temperature, aeration rate, and substrate water content on sporulation of Penicillium roqueforti on buckwheat seeds in a fixed bed reactor is described. Use of an experimental procedure based on a 2³ factorial design allowed optimum to be determined as 23.5° C for temperature, 0.48 g/g dry matter for substrate water content and 4.42 VVH for aeration rate.     

Mixed-solid substrate fermentation. A novel process for enhanced lipase production by Candida rugosa

Candida rugosa was cultivated in a mixed-solid substrate containing coconut oil cake (COC) and fine and coarse wheat bran (1:1:1) with an initial water activity (a_w) of 0.92. The substrate was modified by adding a mineral solution (5%), corn steep liquor (6%), maltose (2%), peptone (3%), olive oil (10%), gum arabic (0.4%), different fatty acids (0.3%) and Tweens (0.5%). Fermentation in a column fermenter significantly improved the lipase yield to 118.2 Units per gram of dry fermented substrate [U/gds] at 72 h. This result was obtained 24 hours earlier than in our former studies (87.76 U/gds at 96 h) in COC, and the yield showed a 38% increase. Growth was measured indirectly by determining the glucosamine content in the cell wall of the yeast contained in the fermented matter, after its hydrolysis.     

Mixed culture solid substrate fermentation for cellulolytic enzyme production

Summary Cellulolytic and hemicellulolytic enzymes were produced on extracted sweet sorghum silage by mixed culture solid substrate fermentation with Trichoderma reesei LM-1 (a Peruvian mutant) and Aspergillus niger ATCC 10864. Optimal cellulose and xylanase levels of 4 IU/g dry weight (DW) and 180 IU/g DW, respectively, were achieved in 120 h-fermentation when T. reesei, inoculated at 0 h, was followed by the inoculation of A. niger at 48 h.     

Biosynthesis of protein by microscopic fungi in solid state fermentation. I. Selection of Aspergillus strain for enrichment of starchy raw materials in protein

A fungal strain suitable for protein enrichment of starchy raw materials was selected by evaluation of the growth rate, results of protein biosynthesis in solid state fermentation (SSF) and assessment of fungal biomass. The strain Aspergillus oryzae A.or. 11 selected for further studies was characterized by the radial growth rate K_r of about 300 μm/h and by the specific growth rate μ of about 0.100 h^?1. Fungal biomass contained about 32% of crude protein in dry matter. The digestibility of this protein in vitro was close to 75%. Protein analysis for amino acids showed that the content of exogenous amino acids approached that in protein of the FAO standard. As a result of 34 — h culture of this strain in solid medium, net protein increased by about 5.0 g/100 g of starting medium d.m. at the cost of decomposition of about 20 g carbohydrates.     

Production of fungal chitosan by solid substrate fermentation followed by enzymatic extraction

An improved method is described for the production of chitosan from mycelia of the fungus Gongronella butleri, grown by solid substrate fermentation on sweet potato. The chitosan was extracted subsequently by 11 M NaOH at 45 °C, and 0.35 M acetic acid at 95 °C. The resulting extract was clarified using a heat-stable, commercial -amylase. The yield (4–6 g/100 g mycelia) and relative number average molecular weight (44–54 kDa) of the chitosan increased with increasing duration of fungal growth up to the sixth day.     

Water and water activity in the solid state fermentation of cassava starch by Aspergillus niger

Summary During the solid state fermentation (SSF) of cassava starch by Aspergillus niger estimations were made of total water, consumed water and the residual water remaining in small quantities after 23 h. A theoretical calculation based on the Ross equation showed that the water activity (a _w) of the substrate decreased to 0.85 towards the end of the culture. Such low values were assumed to be inhibitory to growth. The a _w of the substrate was increased when sugarcane bagasse was used as a high water retention capacity support. Higher growth rates and substrate conversion to biomass were obtained with this system, confirming that water availability is a critical factor in the SSF of starch substrates.Abbreviations A, B Experimental constants - a _w Water activity - H₂O_c Consumed water - H₂O_R Residual water - H₂O_T Total water - IDW Initial dry weight - IMC Initial moisture content - OUR Oxygen uptake rate - S Substrate dry weight - Sc Substrate conversion: consumed substrate/initial substrate - S _H Amount of sugars hydrolysed - SSF Solid state fermentation - X Biomass dry weight - W ^* Amount of solids/g of water     

A pilot process of solid state fermentation from sugar beet pulp for the production of microbial protein

The bioconversion of sugar beet pulp (SBP) into microbial protein by the process of solid state fermentation (SSF) was studied. Two SSF reactors (each having overall dimensions of 17.6 × 3.6 × 2.0 m) with appropriate control systems were constructed. This pilot plant has a maximum working capacity of 50 metric tons (20% dry metter). The production strain used was Aspergillus tamarii 827, which was isolated by our laboratory. The protein content of the products amounted to 22.4% in 48 h.     

Comparative study of protease production in solid substrate fermentation versus submerged fermentation

Attempts have been made to compare solid substrate fermentation (SSF) with submerged fermentation for the production of proteases by Bacillus amyloliquefaciens. In submerged fermentation it produced 800,000 units of enzyme under optimal conditions in a 20-litre fermentor whereas in solid substrate, it produced 250,000 units/g. Owing to the simplicity and easiness of operation of SSF and for applications like unhairing, biodetergents and bating the former would be advantageous for the production of proteases.     

Growth kinetics of Rhizopus arrhizus in solid state fermentation of treated cassava

Summary Growth kinetics of Rhizopus arrhizus MUCL 28168 were determined for different treatments of cassava during solid state fermentation. The best case gave a specific growth rate () of 0.24 h^-1, a yield calculated on a basis that oxygen consumption (Y_x/o) was 2.9 g biomass. g^-1 O₂ consumed and the maintenance coefficient (m) was 0.004 g O₂ consumed. g^-1 biomass. h^-1.