Production of microbial lipases in a solid state fermentation system

Summary Several filamentous fungi were grown on solid state fermentation systems and selected for their highest yield in lipolytic activity, low protease levels and dairy flavor generation.P. candidum,M. miehei andP. camembertii were the selected ones. A comparison between kinetics in solid and submerged fermentation was performed usingP. candidum, with the solid system giving the highest titers and a stable production.     

Production of pectinesterase and polygalacturonase by Aspergillus niger in submerged and solid state systems

Production of pectinesterase and polygalacturonase by Aspergillus niger was studied in submerged and solid-state fermentation systems. With pectin as a sole carbon source, pectinesterase and polygalacturonase production were four and six times higher respectively in a solid state system than in a submerged fermentation system and required a shorter time for enzyme production. The addition of glucose increased pectinesterase and polygalacturonase production in the solid state system but in submerged fermentation the production was markedly inhibited. A comparison of enzyme productivities showed that those determined for pectinesterase and polygalacturonase with pectin as a carbon source were three and five times higher by using the solid state rather than the submerged fermentation system. The productivities of the two enzymes were affected by glucose in both fermentation systems. The membranes of cells from the solid state fermentation showed increased levels of C18:1, C16:0 and C18:0 fatty acids. Differences in the regulation of enzyme synthesis by Aspergillus niger depended on the fermentation system, favoring the solid state over the submerged fermentation for pectinase production. Received 12 May 1997/ Accepted in revised form 19 September 1997     

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.     

Influence of the glycolytic rate on production of citric acid and oxalic acid by Aspergillus niger in solid state fermentation

A study was performed to understand the physiology and biochemical mechanism of citric acid accumulation during solid state fermentation of sweet potato using Aspergillus niger Yang No.2. A low citrate-producing mutant was isolated followed by a comparative study of the fermentation process and selected physiological and biochemical parameters. In contrast with the parent strain, the mutant strain displayed lower concentrations, yields and production rates of citric acid, accompanied by higher concentrations, yields and production rates of oxalic acid. In addition, the mutant utilized starch at a lower rate although higher concentrations of free glucose accumulated in the cultures. Biochemical analyses revealed lower rates of glucose uptake and hexokinase activity of the mutant strain in comparison with the parent strain. It is proposed that, in common with submerged fermentation, over-production of citric acid in solid state fermentation is related to an increased glucose flux through glycolysis. At low glucose fluxes, oxalic acid is accumulated.     

Characterization of a thermostable alpha-amylase from a thermophilic Streptomyces megasporus strain SD12

An extracellular alpha-amylase (1,4-alpha D-glucan glucan hydrolase; EC 3.2.1.1) was isolated from the cell free broth of Streptomyces megasporus SD12 grown in glucose, soluble starch and raw starch. The enzyme was purified 55-fold with a specific activity of 847.33 U mg-1 of protein and with a yield of 36% activity. The apparent molecular mass of the enzyme was 97 kDa, as estimated by SDS-PAGE. The pI of the enzyme was 5.4 and it was stable at a pH range of 5.5 to 8.5 with an optimum pH 6. The enzyme was stable upto 85 degrees C with a half life of 60 min. With soluble starch as substrate the enzyme exhibited a K(m) and kcat value of 4.4 mg ml-1 and 2335 U min-1 mg-1 of protein respectively. The major end products of starch hydrolysis were maltotriose and maltose depending on the incubation period. The production of the enzyme with agricultural wastes as substrates was 643 to 804 U min-1 mg-1 of protein in submerged fermentation whereas solid state fermentation could produce only 206 U min-1 mg-1 of protein.     

Influence of oxygen transfer rate on vinegar production by Acetobacter aceti in submerged fermentation

Summary A study was carried out on the influence of oxygen transfer rate on bacterial growth and acid production in submerged vinegar fermentation by an industrial culture of Acetobacter aceti. The production rate grew as did growth rate even if no increment in cellular mass was noticed when oxygen transfer rate was increased. The relationship between growth and production followed a mixed growth associated model.     

A model substrate for solid-state fermentation

Summary A model substrate consisting of cassava starch embedded in kappa-carrageenan was used to mimic the growth ofRhizopus oligosporus on cassava tubers. Growth on the model substrate was similar to that during solid-state fermentation of the actual cassava. However, protein production and starch utilization were slower on the model substrate.     

Solid state fermentation for production of higher titres of thermostable alpha-amylase with two peaks for pH optima byBacillus licheniformis M27

Summary Bacillus licheniformis M27 produced 21, 000 units of alpha-amylase/g dry bacterial bran under solid state fermentation in wheat bran medium enriched with 3.3% di-ammonium hydrogen phosphate. The crude enzyme, with temperature optimum at 90°C in 0.5% starch solution, showed pH optima at 6.5–7.0 and 9.5 and over 75% activity over the pH range 6.0–10.5.     

Effect of substrate moisture content on fungal production of citric acid in a solid state fermentation system

Summary Under solid state fermentation conditions, the production of citric acid byAspergillus niger varied considerably with the initial moisture content of apple pomace. The stimulating effect of methanol on fungal production of citric acid decreased markedly as the substrate moisture decreased.     

Solid-state fermentation increases secretome complexity in Aspergillus brasiliensis

Aspergillus is used for the industrial production of enzymes and organic acids, mainly by submerged fermentation (SmF). However, solid-state fermentation (SSF) offers several advantages over SmF. Although differences related to lower catabolite repression and substrate inhibition, as well as higher extracellular enzyme production in SSF compared to SmF have been shown, the mechanisms undelaying such differences are still unknown. To explain some differences among SSF and SmF, the secretome of Aspergillus brasiliensis obtained from cultures in a homogeneous physiological state with high glucose concentrations was analyzed. Of the regulated proteins produced by SmF, 74% were downregulated by increasing the glucose concentration, whereas all those produced by SSF were upregulated. The most abundant and upregulated protein found in SSF was the transaldolase, which could perform a moonlighting function in fungal adhesion to the solid support. This study evidenced that SSF: (i) improves the kinetic parameters in relation to SmF, (ii) prevents the catabolite repression, (iii) increases the branching level of hyphae and oxidative metabolism, as well as the concentration and diversity of secreted proteins, and (iv) favors the secretion of typically intracellular proteins that could be involved in fungal adhesion. All these differences can be related to the fact that molds are more specialized to growth in solid materials because they mimic their natural habitat.     

Temperature cycling to improve the ethanol production with solid state simultaneous saccharification and fermentation

Simultaneous saccharification and fermentation (SSF) widely used in submerged state could be effective in solid state. Solid state SSF was first compared with solid state separate hydrolysis and fermentation on ethanol production. Ethanol yield using solid state separate hydrolysis and fermentation (SHF) in 5 days was only half of that in solid state SSF in 3 days. In solid state SSF, the ethanol concentration using temperature cycling (10 h at 37 degrees C followed by 15 min at 42 degrees C) was 2 times that using constant 37 degrees C within 72 h, reached 5.2%.     

Temperature cycling to improve the ethanol production with solid state simultaneous saccharification and fermentation

Simultaneous saccharification and fermentation (SSF) widely used in submerged state could be effective in solid state. Solid state SSF was first compared with solid-state separate hydrolysis and fermentation on ethanol production. Ethanol yield using solid-state separate hydrolysis and fermentation (SHF) in 5 days was only half of that in solid state SSF in 3 days. In solid state SSF, the ethanol concentration using temperature cycling (10 h at 37°C followed by 15 min at 42°C) reached 5.2% which was 2 times higher than that observed at 37°C within 72 h. The text was submitted by the authors in English.     

Production of the antifungal peptide antibiotic,iturin by Bacillus subtilis NB22 in solid state fermentation

Production of iturin, an antifungal peptide effective at suppressing phytopathogens, by Bacillus subtilis NB22 was investigated in solid state fermentation (SSF) using soy bean curd residue (okara). In scale-up from 15 g to 3 kg, aeration, temperature, and moisture content were controlling factors for the efficient production of iturin. It was found that solid state fermentation was 6–8 times more efficient with respect to iturin productivity than submerged fermentation on the basis of unit wet weight. Higher productivity in selective production of specific components of iturin which are stronger inhibitors of plant pathogens was also confirmed in SSF.     

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.     

Selection of preculture conditions for solid state fermentation of sugar beet pulp

Summary For the protein upgrading of sugar-beet pulp in solid state fermentation byTrichoderma reesei andFusarium oxysporum, serveral conditions were studied to prepare an economical preculture for large scale process. The best performance was shown by a preculture obtained in 24 h from 1.5 % molasses solution at pH 4.5–5.0 with 1.0 % milled beet pulp.     

Optimization of fermentation conditions for the production of ethanol from sago starch by co-immobilized amyloglucosidase and cells of Zymomonas mobilis using response surface methodology

Statistical experimental design was used to optimize the conditions of simultaneous saccharification and fermentation (SSF), viz. temperature, pH and time of fermentation of ethanol from sago starch with co-immobilized amyloglucosidase (AMG) and Zymomonas mobilis MTCC 92 by submerged fermentation. Maximum ethanol concentration of 55.3 g/l was obtained using a starch concentration of 150 g/l. The optimum conditions were found to be a temperature of 32.4 °C, pH of 4.93 and time of fermentation of 17.24 h. Thus, by using SSF process with co-immobilized AMG and Z. mobilis cells MTCC 92, the central composite design (CCD) was found to be the most favourable strategy investigated with respect to ethanol production and enzyme recovery.     

固态间歇补料乙醇生料发酵新工艺

浓醪发酵是酒精生产的发展方向。与现行酒精厂普遍采用的热蒸煮工艺相比, 生料发酵技术的发展使得浓醪发酵更容易进行。本研究首次在生料发酵中直接采用固态原料间歇补料, 比较了STARGENTM生淀粉水解酶间歇补料工艺和传统无补料工艺, 并对不同补料方式进行了研究。结果表明: 与传统无补料生料发酵工艺相比, 在相同的干基配料浓度30%、相同的生料酶添加量0.22%(W/W)的条件下, 采用15%的起始配料浓度、发酵15~25 h进行间歇补料的新工艺, 酒精产量从17.06%提高到18.50%。该间歇补料优化工艺的建立, 丰富了生料发酵技术的应用。     

Production of Aspergillus terreus alpha-L-rhamnosidase by solid state fermentation

AIMS: The study of production of Aspergillus terreus CECT 2663 alpha-L-rhamnosidase in solid state fermentation using wheat bran, washed sugar cane bagasse and polyurethane foam as substrates or supports for the enzyme production. METHODS AND RESULTS: Cultures were carried out in Petri dishes under controlled temperature and humidity. Naringin or rhamnose were the enzyme inducers and carbon sources. The enzyme activity to inducer ratio was appreciably greater when using sugar cane bagasse or polyurethane foam than wheat bran. The influence of inoculum size, inducer, airflow, humidity and temperature were determined. Under optimum conditions, about four units of enzyme per ml nutrient solution were obtained after 4-6 d. CONCLUSIONS: The activity to inducer ratio was higher, and the cultivation time was shorter in solid state fermentation than those observed in submerged cultures. SIGNIFICANCE AND IMPACT OF THE STUDY: Solid cultures, using naringin as inducer, can be appropriate alpha-L-rhamnosidase production.     

Enhanced cellulase production using Solka Floc in a fed-batch fermentation

Summary Use of a fed-batch mode of cultivation of T. reesei has permitted high concentrations of substrate to be consumed. This has resulted in the production of high titre cellulase preparations around 30 FPU/ml at high volumetric productivities (177 IU/L.hr).Perhaps the most obvious area for major improvement in the process of cellulose utilization is the production of cellulase enzyme for hydrolysis of wood and agricultural residues. It has been estimated that some 50% of the cost of producing glucose from cellulosic material is attributable to enzyme production alone (Perez, et al., 1980). Improvements in the area would therefore have a dramatic impact, and are of paramount importance if economical hydrolysis processes are to be realized. The first major thrust in the area has been the development of improved mutant strains of T. reesei, free from catabolite repression and capable of constitutive cellulase production (Montenecourt and Eveleigh, 1977; Gallo, 1982).While this effort continues to develop further high yielding mutants, improvement must also come from developments in fermentation techniques. A major advance is the use of fed-batch cultivation, which provides a means of avoiding the agitation and aeration difficulties, as well as repression effects encountered with high substrate concentration batch fermentation. This report briefly compares batch and fed-batch operation over a range of substrate concentrations.     

Kinetics of rice straw methane fermentation

Summary The kinetics of anaerobic fermentation of rice straw to methane were studied. Rice straw was the only carbon source at influent volatile solid concentrations of 18.9 and 37.8 g/l. Semicontinous runs were carried out at 37°C in laboratory scale perfectly mixed reactors. The Contois' kinetic model constants were calculated from the experimental data. Arefrac tory coefficient was measured (R=0.374) to account for the nonbiodegradable portion of the organic matter of rice straw and incorporated into the kinetic equations. The predicted values of effluent substrate concentration, volumetric methane yield, volumetric methane production rate, and biodegradable conversion efficiency fit well with those measured experi mentally.Percent destruction values of feed constituents were measured.