Advantages of fungal enzyme production in solid state over liquid fermentation systems

The present paper attempts to explain why enzyme production in solid-state fermentation (SSF) is higher than in submerged fermentation (SmF). Recent work done in our laboratory [Biotechnol. Lett. 22 (2000) 1255; J. Ind. Microbiol. Biotechnol. 26 (5) (2001) 271; J. Ind. Microbiol. Biotechnol. 26 (5) (2001) 296] related to the production of invertase, pectinases and tannases, by Aspergillus niger grown by SSF and SmF is reviewed. To do such a comparative study, logistic and Luedeking–Piret equations are used in order to estimate the values of the following coefficients: maximal specific growth rate (μ_M), maximal biomass level (X_M), enzyme/biomass yield (Y_P/X) and secondary rate of production, or breakdown (k). It is shown that enzyme productivity is proportional to group, μ_MY_P/XX_M, corrected by a function of ν=k/Y_P/Xμ_M. In all three cases of enzyme production studied, productivity using a SSF system was higher than in SmF. Studies with invertase resulted in higher values of μ_MX_M. Studies with pectinases resulted in higher values of Y_P/XX_M. Studies with tannases resulted in higher Y_P/X and less negative values of k. Finally, a reaction–diffusion model is presented to try to explain such differences based on micrographic measurements of mycelial aggregates for each kind of fermentation system.     

Penicillin production by solid state fermentation

Summary Penicillin was produced by a non-sterile solid state fermentation (SSF) on bagasse impregnated with culture medium. The use of concentrated media greatly enhanced the antibiotic production in this system. It was observed that adequate initial moisture content (70%) of the impregnated solid medium results in higher production. A comparison between solid and liquid fermentation showed superior yield and productivity.     

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.     

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.     

白腐菌液体和固体培养产生木质纤维素降解酶的比较研究

侧耳sp2(Pleurotus sp．2)和粗毛栓菌(Trametes gallica)是产木质纤维素降解酶能力强,且产酶较快的菌株。对其在液体培养基、固体培养基中产生木质纤维素降解酶能力和行为进行了比较分析和研究。结果表明,Pleurotus sp．2在低氮高碳高无机盐培养基中的锰过氧化物酶(Manganese peroxidases, MnPs)、木质素过氧化物酶(Lignin peroxidases．LiPs)、漆酶(laccases,Lacs)和半纤维素酶(Hemicellulases, Hcels)的活性最高。当该菌株培养在含有低氮无碳高无机盐液体培养基的麦草粉中时,MnPs和Lacs的活性峰值均出现在10d,而Hcels的活性在40d时达到峰值。Trametes gallica在高氮低碳高无机盐培养基中的Lacs和LiPs的活性最高,在低氮高碳高无机盐培养基中的MnPs和Hcels的活性最高。当该菌株培养在含有高氮无碳高无机盐和低氮无碳高无机盐液体培养基的麦草粉中时,MnPs存10d、Lacs和Hcels在40d、LiPs存50d,分别达到峰值。Pleurotus sp．2和Trametes gallica在液体培养基中具有很强的木质纤维素降解酶产生能力且产酶速度较快,在固体培养基中具有很强的降解麦秸生物质能力,但这两株菌在液体和固体培养基中,产木质纤维素降解酶的能力和行为都有较大的差异,相关性小。     

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.     

Thermophilic,lignocellulolytic bacteria for ethanol production: current state and perspectives

Lignocellulosic biomass contains a variety of carbohydrates, and their conversion into ethanol by fermentation requires an efficient microbial platform to achieve high yield, productivity, and final titer of ethanol. In recent years, growing attention has been devoted to the development of cellulolytic and saccharolytic thermophilic bacteria for lignocellulosic ethanol production because of their unique properties. First of all, thermophilic bacteria possess unique cellulolytic and hemicellulolytic systems and are considered as potential sources of highly active and thermostable enzymes for efficient biomass hydrolysis. Secondly, thermophilic bacteria ferment a broad range of carbohydrates into ethanol, and some of them display potential for ethanologenic fermentation at high yield. Thirdly, the establishment of the genetic tools for thermophilic bacteria has allowed metabolic engineering, in particular with emphasis on improving ethanol yield, and this facilitates their employment for ethanol production. Finally, different processes for second-generation ethanol production based on thermophilic bacteria have been proposed with the aim to achieve cost-competitive processes. However, thermophilic bacteria exhibit an inherent low tolerance to ethanol and inhibitors in the pretreated biomass, and this is at present the greatest barrier to their industrial application. Further improvement of the properties of thermophilic bacteria, together with the optimization production processes, is equally important for achieving a realistic industrial ethanol production.     

Effect of culture conditions on lipolytic enzyme production by Penicillium candidum in a solid state fermentation

Lipolytic enzymes were produced using wheat bran as substrate in a solid state fermentation with Penicillium candidum. The best production of lipolytic activity occurred at 29 degrees C. One hundred micromoles of free butyric acid (FBA) was released from tributyrin by 1 mL of cell free supernatant in the absence of control of environmental relative humidity. When a closed chamber saturated with water vapour was used the lipolytic activity increased to 320 micromoles of free butyric acid. The best initial reaction pH was 7.0. The highest activity, 480 micromoles of FBA, was obtained at a moisture content of 67.5 % of saturation.     

Cyclosporin-A production by Tolypocladium inflatum using solid state fermentation

Tolypocladium inflatum strains are known to produce Cyclosporin-A under submerged culture conditions. In the present study solid state fermentation was used to produce Cyclosporin-A. Tolypocladium inflatum strains when grown on moist wheat bran produced 310–459 mg of Cyclosporin-A kg of bran⁻¹. Tolypocladium inflatum ATCC 34921 which produced 459 mg of Cyclosporin-A kg of bran⁻¹ was improved to produce 1031±27 mg of Cyclosporin-A kg⁻¹ of bran, by subjecting the spores to different mutagenic treatments. The mutated strain, designated Tolypocladium inflatum DRCC 106, produced 4843 mg kg⁻¹ of bran under optimum fermentation conditions in 10 days when grown on wheat bran medium containing millet flour 20%, jowar flour 10%, zinc sulphate 0·15%, ferric chloride 0·25% and cobaltous chloride 0·05%. An inoculum of 60% initial moisture content 70%, initial bran pH 2·0 and incubation temperature 25°C were found to be optimal. Cyclosporin-A thus obtained was purified by solvent extraction, followed by column chromatography. The isolated product complies with the United States Pharmacopoeia specifications.     

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.     

Phytase production by a thermophilic mould Sporotrichum thermophile in solid state fermentation and its potential applications

Phytase production by a thermophilic mould Sporotrichum thermophile Apinis was investigated in solid state fermentation (SSF) using sesame oil cake as the substrate. Scanning electron microscopy of the fermented sesame oil cake revealed a dense growth of the mould with abundant conidia. Glucose, ammonium sulphate and incubation period were identified as the most significant factors by Plackett-Burman design. The optimum values of the critical components determined by central composite design of response surface methodology for the maximum phytase production were glucose 3%, ammonium sulphate 0.5% and incubation period 120 h. An overall 2.6-fold improvement in phytase production was achieved due to optimization. Highest enzyme production (348.76 U/g DMR) was attained at a substrate bed depth of 1.5 cm in enamel coated metallic trays. The enzyme liberated inorganic phosphate from wheat flour and soymilk with concomitant dephytinization and liberation of soluble inorganic phosphate.     

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     

Bioreactor designs for solid state fermentation

Solid state fermentation has gained renewed attention not only from researchers but also from industry. This technique has become a more and more attractive alternative to submerged fermentation for specific applications due to the recent improvements, especially in the design. This paper reviews the various reactor designs and focuses on the differences between lab-scale and industrial-scale designs. It highlights the main designs that have emerged over the last 10 years and the potential for scaling-up for each category of reactor.     

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.     

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.     

Citric acid production by solid state fermentation using sugarcane bagasse

A solid state fermentation (SSF) method was used to produce citric acid by Aspergillus niger DS 1 using sugarcane bagasse as a carrier and sucrose or molasses based medium as a moistening agent. Initially bagasse and wheat bran were compared as carrier. Bagasse was the most suitable carrier, as it did not show agglomeration after moistening with medium, resulting in better heat and mass transfer during fermentation and higher product yield. Different parameters such as moisture content, particle size, sugar level and methanol concentration of the medium were optimised and 75% moisture level, 31.8 g sugar/100 g dry solid, 4% (v/w) methanol and particles of the size between 1.2 and 1.6 mm were found to be optimal. Sucrose and clarified and non-clarified molasses medium were also tested as moistening agents for SSF and under optimised conditions, 20.2, 19.8 and 17.9 g citric acid /100 g of dry solid with yield of 69.6, 64.5 and 62.4% (based on sugar consumed) was obtained in sucrose, clarified and non-clarified molasses medium respectively, after 9 days of fermentation.     

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.