A mathematical model for solid state fermentation in tray bioreactors

A simple mathematical model for the interaction of mass transport with biochemical reaction in solid state fermentations (SSF) in static tray type bioreactors under isothermal conditions has been developed. The analysis has enabled scientific explanations to a number of practical observations, through the concept of critical substrate bed thickness. The model will be most useful in the prediction of the concentration gradients as also in efficient design of these bioreactors.List of Symbols C g/cm³ Oxygen concentration in the bed - C _g g/cm³ Atmospheric oxygen concentration - C ^* Dimensionless oxygen concentration, C/C _g - D _e cm²/h Effective diffusivity - H cm Bed thickness or height - H _c cm Critical bed thickness or height - H _m cm Maximum height of zone of zero oxygen concentration - p _i mg/(g · h) Productivity (Eq. 13) - R g/(cm³ · h) Biochemical reaction rate - t h Fermentation time - t ^* Dimensionless time, D _e t/H² - X mg/cm³ Biomass concentration - X _max mg/cm³ Maximum biomass concentration - y Dimensionless thickness or height, (y = z/H) - y cm Thickness of zone of zero oxygen concentration (Eq. 12) - Y Yield coefficient - z cm Bed thickness or height along tray axis - Bed void fraction - _max h^–1 Specific growth rate - Thiele modulus      

Algal biomass: A sustainable,economical and renewable approach for microbial production of pectinolytic enzymes using submerged and solid state fermentation techniques

In the past decade, algal waste has been used as useful natural resource for production of enormous range of products that have wide economical and commercial importance. Pectinases are group of enzymes that have wide commercial applications. Hence, current study was designed to utilize algal biomass for the production of pectinases using submerged (SmF) and solid state fermentation (SSF) techniques. Different algal sources including brown (Dictyopteris polypodioides, Sargassum wightii and Dictyopteris divaricata) and green algae (Ulva lactuca and Codium tomentosum) were used and U. lactuca was found to be the most suitable substrate. Several bacterial and fungal strains were screened and among them Bacillus licheniformis KIBGE-IB4 was selected based on maximum pectinase production. SmF and SSF were studied utilizing U. lactuca as a substrate and results revealed that enzyme production was favoured by SmF (2457?±?3.31?U?mg^?1) as compared to SSF (1432?±?1.46?U?mg^?1). Parametric optimization of pectinase production indicated that B. licheniformis KIBGE-IB4 requires 10.0?g L^–1 U. lactuca as a biomass in the medium with a pH 7.0 when incubated at 37?°C for 24 hours. Likewise, production of pectinase using algal resource was also compared with that of the conventional agricultural biomass and it was observed that when U. lactuca was used, the selected bacterial isolate produced a higher yield of enzyme than sugarcane bagasse and rice husk. Hence, it is anticipated that algal biomass can be efficiently utilized as an environmental friendly bioresource for the production of industrially important hydrolytic enzymes.     

Potential of solid state fermentation for production of ergot alkaloids

Production of total ergot alkaloids by Claviceps fusiformis in solid state fermentation was 3.9 times higher compared to that in submerged fermentation. Production was equal in the case of Claviceps purpurea but the spectra of alkaloids were advantageous with the use of solid state fermentation. The data establish potential of solid state fermentation which was not explored earlier for production of ergot alkaloids.     

Optimization studies on the production of cyclosporin A by solid state fermentation

Several parameters including (a) tray fermentation with and without perforation (b) thickness of solid substrate bed (c) type of inoculum (d) size of inoculum (e)?effect of relative humidity were studied for the optimum production of Cyclosporin A by solid state fermentation using Tolypocladium sp. The results indicate that while perforations in the trays had no significance on the yield of Cyc A, the other parameters had an influence on the production of Cyc A. The results indicate that under the optimized conditions, Cyc A can be produced in bulk quantities economically.     

Biomass estimation in solid state fermentation II. On-line measurements

Summary Two methods for on-line biomass measurement were tested with success: (a) infrared (IR) estimation of cell components (glucosamine and ergosterol) and medium residues (sucrose and nitrogen) directly on solid medium; (b) the CO₂ evolution rate during cultivation. These methods were very satisfactory for following biomass changes during a defined process. The IR measurements correlated well with manual methods. The correlation between CO₂ and glucosamine measurements was very satisfactory with good precision. However, they did not permit comparison between processes.Offprint requests to: C. Desgranges     

alpha-Amylase production by solid state fermentation: a new practical approach to biotechnology courses

A laboratory practical experiment in Biotechnology involving the investigation of alpha-amylase production by solid state fermentation of Gibberella fujikuroi is described.     

Economic production of Lysinibacillus sphaericus under solid state fermentation

A highly active mosquitocidal Lysinibacillus sphaericus namely Ls 9B24 was isolated from soil of Alexandria governorate in Egypt. It was more active than the standard strain, L. sphaericus 2362. The sporulation and toxin formation of both cultures grown on different leguminous seeds and by-products under solid state fermentation (SSF) were studied. Among the tested substrates, 6% cotton seed meal enhanced sporulation and the mosquitocidal activity of L. sphaericus 2362, while 6% fodder yeast enhanced sporulation and the mosquitocidal activity of Ls 9B24. The optimum SSF growth conditions for maximum mosquitocidal activity by both cultures were using coarse wheat bran as a carrier material, 50% initial moisture content, 4–64 × 10⁶ colony forming units (CFU)/g solid medium inoculum and 6 days’ incubation period at 30°C. Addition of 0.5% yeast extract enhanced toxicity about 2.2 and 1.8 fold for L. sphaericus 2362 and Ls 9B24, respectively.     

Biomass estimation in solid state fermentation I. Manual biochemical methods

Summary We examined the changes in three biomass constituents (glucosamine, ergosterol, total sugar), sucrose consumption and conidia formation, during cultivation of Beauveria bassiana on agar plates or clay granules. We showed that glucosamine can be considered a good biomass indicator on condition that the media had the same constituents but not necessarily the same C/N ratio. Total sugar was not constant during the different growth phases and cannot accurately represent biomass changes. The ergosterol amounts changed during the different growth phases but, for a fixed process, it can be a good indicator of conidiation. Good correlations were obtained between glucosamine and sucrose consumption allowing biomass yield calculations.Offprint requests to: C. Desgranges     

Microbiological fermentation of lignocellulosic biomass: current state and prospects of mathematical modeling

The anaerobic fermentation process has achieved growing importance in practice in recent years. Anaerobic fermentation is especially valuable because its end product is methane, a renewable energy source. While the use of renewable energy sources has accelerated substantially in recent years, their potential has not yet been sufficiently exploited. This is especially true for biogas technology. Biogas is created in a multistage process in which different microorganisms use the energy stored in carbohydrates, fats, and proteins for their metabolism. In order to produce biogas, any organic substrate that is microbiologically accessible can be used. The microbiological process in itself is extremely complex and still requires substantial research in order to be fully understood. Technical facilities for the production of biogas are thus generally scaled in a purely empirical manner. The efficiency of the process, therefore, corresponds to the optimum only in the rarest cases. An optimal production of biogas, as well as a stable plant operation requires detailed knowledge of the biochemical processes in the fermenter. The use of mathematical models can help to achieve the necessary deeper understanding of the process. This paper reviews both the history of model development and current state of the art in modeling anaerobic digestion processes.     

Culture requirements for the production of protease by Aspergillus oryzae in solid state fermentation

Summary A number of culture conditions for protease production by Aspergillus oryzae NRRL 2160 on solid substrates were investigated. The pH of the medium and the substrate markedly affected protease production. High protease yield was obtained when the fungus was cultivated for 72–96 h on rice hulls: rice bran (7:3), at an initial pH of 7.0. Maximal protease production was achieved at an initial moisture content of 35–40%, corresponding to a water activity range of 0.982–0.986. Casein and gluten were effective inducers. Polyethylene bags proved to be promising containment systems for solid state cultivation.Offprint requests to: A. M. R. Pilosof     

Extracellular xylanase production by Fusarium species in solid state fermentation

Fusarium sp. has been shown to be a promising organism for enhanced production of xylanases. In the present study, xylanase production by 21 Fusarium sp. isolates (8 Fusarium culmorum, 4 Fusarium solani, 6 Fusarium verticillioides and 3 Fusarium equiseti) was evaluated under solid state fermentation (SSF). The fungal isolate Fusarium solani SYRN7 was the best xylanase producer among the tested isolates. The effects of some agriculture wastes (like wheat straw, wheat bran, beet pulp and cotton seed cake) and incubation period on xylanase production by F. solani were optimized. High xylanase production (1465.8 U/g) was observed in wheat bran after 96 h of incubation. Optimum pH and temperature for xylanase activity were found to be 5 and 50 degrees C, respectively.     

Enhanced lovastatin production by solid state fermentation ofMonascus ruber

The purpose of this study was to optimize the solid state cultivation ofMonascus ruber on sterile rice. A single-level-multiple-factor and a single-factor-multiple-level experimental design were employed to determine the optimal medium constituents and to optimize carbon and nitrogen source concentrations for lovastatin production. Simultaneous quantitative analyses of the β-hydroxyacid form and β-hydroxylactone for of lovastatin were performed by the high performance liquid chromatography (HPLC) method with a UV photodiode-array (PDA) detector. The total lovastatin yield (4≈6 mg/g, average of five repeats) was achieved by adding soybean powder, glycerol, sodium nitrate, and acetic acid at optimal composition of the medium increased by almost 2 times the yield observed prior to optimization. The experimental results also indicated that the β-hydroxylactone form of lovastatin (LFL) and the β-hydroxyacid form of lovastatin (AFL) simultaneously existed in solid state cultures ofMonascus ruber, while the latter was the dominant form in the middle-late stage of continued fermentation. These results indicate that optimized culture conditions can be used for industrial production of lovastatin to obtain high yields.     

Spore production ofPenicillium roqueforti by simulated solid state fermentation

Summary A culture technique, based on the growth of a microorganism on inert porous particles (e. g. pozzolano) impregnated and continuously fed with substrate is applied to the growth and spore production ofPenicillium roqueforti. The composition and the feed rate of the medium can be controlled, and the biomass is directly estimated.P. roqueforti exhibits a diauxic growth on the medium containing sucrose and malt extract used, and 1.5 10⁹ spores/g pozzolano may be obtained.     

Potential of fed-batch culture in solid state fermentation for production of gibberellic acid

Summary Fed-batch culture technique, applied to the solid state fermentation process for the production of gibberellic acid, improves the yield by 18.2% as compared to a conventional batch solid state fermentation.     

Utilisation of fruits waste for citric acid production by solid state fermentation

A solid state fermentation method was used to utilise pineapple, mixed fruit and maosmi waste as substrates for citric acid production using Aspergillus niger DS 1. Experiments were carried out in the presence and absence of methanol at different moisture levels. In the absence of methanol the maximum citric acid was obtained at 60% moisture level whereas in the presence of methanol the maximum citric acid was obtained at 70% moisture level. The stimulating effect of methanol was less at lower moisture level. The inhibitory effect of metal ions was also not observed and maximum citric acid yield of 51.4, 46.5 and 50% (based on sugar consumed) was obtained from pineapple, mixed fruit and maosmi residues, respectively.     

Microbial production of gallic acid by modified solid state fermentation

Bioconversion of tannin to gallic acid from powder of teri pod (Caesalpinia digyna) cover was achieved by the locally isolated fungus, Rhizopus oryzae, in a bioreactor with a perforated float for carrying solid substrate and induced inoculum. Modified Czapek-Dox medium, put beneath the perforated float, with 2% tannic acid at pH 4.5, temperature 32°C, 93% relative humidity, incubated for 3 days with 3-day-old inoculum was optimum for the synthesis of tannase vis-à-vis gallic acid production. Conversion of tannin to gallic acid was 90.9%. Diethyl ether was used as the solvent for extraction of gallic acid from the fermented biomass. Received 14 December 1998/ Accepted in revised form 17 June 1999     

Biomass estimation in solid state fermentation by modeling dry matter weight loss

The mathematical model introduced by Okazaki & Tanaka (J. Ferment Technol. 1980, 58: 471–476) for estimating fungal growth in solid state fermentations by CO2 evolution, was incorporated into a relationship developed to estimate biomass growth from dry matter weight loss. The proposed equation fitted experimental data very well (R2=0.987, P<0.0001) and allowed accurate predictions of fungal specific growth rate and maximal biomass in the solid substrate fermentation system.     

Tetracycline production with sweet potato residue by solid state fermentation

For saving energy in antibiotic production and reducing the amount of agricultural wastes, solid state fermentation was used in this study to produce tetracycline with sweet potato residue by Streptomyces viridifaciens ATCC 11989. It was found that the optimal media for tetracycline production were sweet potato residue 100 g, organic nitrogen (rice bran, wheat bran, or peanut meal) 20 g, (NH(4))(2)SO(4) 2.4 g, KH(2)PO(4) 0.4 g, CaCO(3) 1.8 g, NaCl 0.6 g, MgCl(2) 0.8 g, soluble starch 10 g, methionine 0.2 g, histidine 0.8 g, and monosodium glutamate 1.6 g with initial moisture content 68-72%, and initial pH 5.8-6.0. Each gram of dry weight substrate was inoculated with 1.0 x 10(8) conidia and incubated at 26 degrees C for 5-7 days, producing 4720 mug of total tetracycline equivalent potency. When incubated at 26 degrees C with the initial moisture content 68%, the conidia in solid media germinated on the second day, mycelia grew abundantly on the third day and reached stationary phase on the sixth day. The antibiotic production was consistent with the morphogenesis of S. viridifaciens: activity could be detected on the third day, had the maximal potency on the sixth day, and decreased slightly on the tenth day. (11-3-88 tly).     

Optimizing some factors affecting protease production under solid state fermentation

Production of extracellular alkaline protease by a locally isolated fungal species, Rhizopus oryzae, under solid state fermentation was optimized. The maximum enzyme activity under the optimum conditions of temperature (32?°C), relative humidity (90%–95%), spore count (～2?×?10⁵/g wheat bran), moisture content of solid substrate (140%) adjusted suitably with salt solution (M-9) of pH?5.5 was 341 unit/g wheat bran.