Production and properties of three pectinolytic activities produced byAspergillus niger in submerged and solid-state fermentation

Three extracellular pectinases were produced byAspergillus niger CH4 by submerged and solid-state fermentation, and their physicochemical and kinetic properties were studied. The highest productivities of endo- and exo-pectinase and pectin lyase were obtained with solid-state fermentation. The kinetic and physicochemical properties of these enzymes were influenced by the type of culture method used. All activities were very different in terms of pH and temperature optima, stability at different pH and temperature values and affinity for the substrate (K _m values). In solid-state fermentation, all pectinase activities were more stable at extreme pH and temperature values but theK _m values of endo-pectinase and pectin lyase were higher with respect to those activities obtained by the submerged-culture technique. The pectin lyase activity obtained by the submerged-culture technique showed substrate inhibition but the enzyme obtained by solid-state fermentation did not. Electrophoresis, using sodium dodecyl sulphate/polyacrylamide gel with enzymatic extracts obtained for both culture methods, showed the same number on protein bands but some differences were found in their electrophoretic position. The results obtained in this work suggest that the culture method (submerged or solid-state) may be responsible for inducing changes in some of the pectinolytic enzymes produced byA. niger.     

Mathematical modeling of ethanol production in solid-state fermentation based on solid medium’ dry weight variation

In this work, mathematical modeling of ethanol production in solid-state fermentation (SSF) has been done based on the variation in the dry weight of solid medium. This method was previously used for mathematical modeling of enzyme production; however, the model should be modified to predict the production of a volatile compound like ethanol. The experimental results of bioethanol production from the mixture of carob pods and wheat bran by Zymomonas mobilis in SSF were used for the model validation. Exponential and logistic kinetic models were used for modeling the growth of microorganism. In both cases, the model predictions matched well with the experimental results during the exponential growth phase, indicating the good ability of solid medium weight variation method for modeling a volatile product formation in solid-state fermentation. In addition, using logistic model, better predictions were obtained.     

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.     

Growth behaviour of filamentous fungi with varying N supply

Investigations simulating solid-state fermentation, SSF, were carried out to study the influence of a varying N supply on the growth of a mycelium. Experiments with two fungi and two N sources demonstrated the high adaptability of the mycelium to a deficit of nitrogen over a wide range of N supplies. The mycelium of the fungi Gliogladium sp. and Aspergillus sp. can grow up to the very low crude protein content of 11–15%. But protein-poor biomass could not make up the deficit of protein even under optimal cultivation conditions, that means the state of the mycelium remains irreversible. This showed the limit of the adaptability of filamentous fungi, which has to be taken into account for mycelium growth in SSF.     

Effect of the sugar-beet pulp water activity on the solid-state culture of Trichoderma viride TS

Summary The growth and the sporulation of Trichoderma viride TS in relation to water activity (a _w) of sugar-beet pulp medium was studied. It was found that the maximum growth, monitored by protein production, substrate utilization and pH alteration, appeared at a _w=0.990–0.992. Optimal water activity of the medium for sporogenesis was 0.980. It was observed that both physiological phenomena appeared in narrow ranges of water activity which caused the rigorous a _w control in solid-state fermentation to be postulated.     

Cellulase production by Aspergillus niger in biofilm, solid-state, and submerged fermentations

Cellulase production by Aspergillus niger was compared in three different culture systems: biofilm, solid-state, and submerged fermentation. Biofilm and solid-state fermentations were carried out on perlite as inert support, and lactose was used as a carbon source in the three culture systems. In cryo-scanning electron microscopy, biofilm and solid-state cultures gave similar morphological patterns and confirmed that both spore first attachment and hyphal adhered growth are helped by the production of an adhesive extracellular matrix. Biofilm cultures produced higher cellulase activities than those in submerged and solid-state cultures (1,768, 1,165, and 1,174 U l⁻¹, respectively). Although biofilm cultures grew less than the other cultures, they produced significantly higher cellulase yields (370, 212, and 217 U g⁻¹ lactose, respectively) and volumetric productivities (24, 16, and 16 U l⁻¹ h⁻¹, respectively). Likewise, endoglucanase and xylanase activities were higher in biofilm cultures. Under the conditions tested, it seems that fungal attached growth on perlite may favor better enzyme production. Biofilms are efficient systems for cellulase production and may replace solid-state fermentation. Biofilm fermentation holds promise for further optimization and development. The results of this work reveal that fungal biofilms may be used for the commercial production of cellulase employing the technology developed for submerged fermentation at high cell densities.     

Biosynthesis of tannin acyl hydrolase from tannin-rich forest residue under different fermentation conditions

Caesalpinia digyna, a tannin-rich forest residue, was used as substrate for production of tannase and gallic acid. Media engineering was carried out under solid-state fermentation, submerged fermentation and modified solid state fermentation conditions for optimum synthesis of tannase and gallic acid (based on 58% tannin content in the raw material). Tannase vis-à-vis gallic acid recovery under modified solid-state fermentation condition was maximum. Conversions of tannin to gallic acid under solid-state fermentation, submerged fermentation and modified solid-state fermentation conditions were 30.5%, 27.5% and 90.9%, respectively. Journal of Industrial Microbiology & Biotechnology (2000) 25, 29–38. Received 02 November 1999/ Accepted in revised form 12 February 2000     

An enzyme-linked immunosorbent assay for the estimation of fungal biomass during solid-state fermentation

An enzyme-linked immunosorbent assay for sensitive, specific and quantitative estimation of fungal biomass during solid-state fermentation is described. Using this method, differential growth rates and colonization of the substrate can be studied. The assay has potential application for the efficient monitoring of solid-state fermentation involving specific fungus, for which available methods are not adequate. Received: 18 November 1997 / Received last revision: 8 June 1998 / Accepted: 14 June 1998     

Suppression of penetrative hyphae ofRhizopus oligosporus by membrane filters in a model solid-state fermentation system

Summary Membrane filters overlaid on slabs of a model solid substrate enabled recovery of biomass ofRhizopus oligosporus. Although the presence of the membrane filter affects the growth ofRhizopus oligosporus it provides a useful tool for studying solid-state fermentation.     

Optimization of solid-state fermentation of citrus dried peel by aspergillus niger in a packed bed column

The protein enrichment of citrus dried peel on solid-state fermentation by Aspergillus niger in packed bed column was optimized using a two factor central composit design with α = 2 considering the “initial moisture content of the fermentation mass” and the “temperature in the centre of the fermenter”. It results significance for the moisture content (optimum 56%) and non significance for the temperature in the conditions employed. This indicates that a considerable range of temperature increase for the investigated SSF system could be allowed.     

Solubilisation and mineralisation of [14C]lignocellulose from wheat straw by Streptomyces cyaneus CECT 3335 during growth in solid-state fermentation

Nine Streptomyces strains were screened for their ability to solubilise and mineralise ¹⁴C-labelled lignin during growth in solid-state fermentation. Streptomyces viridosporus was confirmed as an active lignin-degrading organism along with a new isolate, Streptomyces sp. UAH 15, further classified as Streptomyces cyaneus CECT 3335. This organism was able to solubilise and mineralise the [¹⁴C]lignin fraction of lignocellulose (44.96 ± 1.77% and 3.41 ± 0.48% respectively) after 21 days of incubation. Cell-free filtrates from Streptomyces sp. grown in solid-state fermentation were capable of solubilising up to 20% of the [¹⁴C]lignin after 2 days incubation, with most of the product detected in the acid-soluble rather than in the water-soluble fraction. Identification of the extracellular enzymes produced during growth of S. cyaneus CECT 3335 revealed that extracellular peroxidase and phenol oxidase activities were present, with the activity of phenol oxidase being 100 times greater than peroxidase activity. The activity of these two enzymes was found to correlate with both solubilisation and mineralisation rates. This is the first report of phenol oxidase activity produced by a Streptomyces strain during growth in solid-state fermentation. A role for the enzyme in the solubilisation and mineralisation of lignocellulose by S. cyaneus is suggested. Received: 12 May 1997 / Accepted: 19 May 1997     

Protein enrichment of apple pomace by co-culture of cellulolytic moulds and yeasts

The co-culture of cellulolytic moulds and yeasts on apple pomace in solid-state fermentation (SSF) and liquid-state fermentation (LSF) increased the protein content of apple pomace. The co-culture of Candida utilis and Aspergillus niger was the best among several combinations and increased the protein content of dried and pectin-extracted apple pomace to 20% and 17%, respectively, under SSF conditions.The authors are with the Microbiology Research Laboratory, Department of Biosciences, Himachal Pradesh University, Shimia-171005, India.     

固态发酵降低上部低次烟叶中淀粉及蛋白质的含量

利用固态发酵的方法降低上部低次烟叶中淀粉和蛋白质的含量,并对发酵过程中的厌氧细菌和酵母的数量进行检测。采用单因素和正交试验对固态发酵的条件进行优化,结果表明:各因素对发酵上部低次烟叶影响显著性主次次序依次为发酵时间(C)、发酵温度(A)和发酵水分质量分数(B),固态发酵的最佳条件为A2B2C3,即温度45℃、水分质量分数50%、发酵时间9 d。在该发酵条件下,上部低次烟叶的淀粉降解率为20.41%,蛋白质降解率为12.35%。通过固态厌氧发酵的方法可取得较好的、短期内快速降解上部低次烟叶中淀粉和蛋白质含量的效果。     

Submerged fermentation in wheat substrates for production of Monascus pigments

Cereal grains are normally used as solid substrates for the production of Monascus metabolites. However, solid fermentation in these substrates requires complex control systems, whereas in liquid culture the control of the fermentation is simpler and consequently significant reductions in fermentation times can be achieved. In the same way, the use of submerged culture can benefit the production of many secondary metabolites and decrease production costs by reducing the labour involved in solid-state methods. A flour composed of a mixed variety of Canadian hard wheat was used as sole nutrient source to produce the pigments of Monascus purpureus Went (IMI 210765). Supplementation with NH₄Cl promoted biomass and orange dye formation, whereas the use of zinc sulphate favoured red dyes production. In submerged fermentations significant differences in final pigment yields were observed in the use of wheat-based broth at different concentrations in the presence of bran particles and/or gluten protein. It has been found that the viscosity of the broth had a significant effect on the growth morphology and production of pigments. Gluten-free wheat flour at concentrations of 3–5% was found to be the most suitable for liquid Monascus culture. The subsequent use of passive immobilization of Monascus served to enhance red pigment yields and to facilitate the downstream processing of the dyes.     

A novel solid-state fermentation system using polyurethane foam as inert carrier

Summary A novel solid-state fermentation method using polyurethane foam as inert carrier impregnated with a synthetic liquid medium was developed simulating the nutritional composition and culture conditions of solid-state fermentation on wheat bran. With this system, biomass, the important parameter involved in solid-state fermentation processes, can be measured directly. Some other superiorities of this system over conventional solid-state fermentation systems are discussed.     

Growth and laccase production by Pleurotus ostreatus in submerged and solid-state fermentation

Pleurotus ostreatus showed atypical laccase production in submerged vs. solid-state fermentation. Cultures grown in submerged fermentation produced laccase at 13,000 U l⁻¹, with a biomass production of 5.6 g l⁻¹ and four laccase isoforms. However, cultures grown in solid-state fermentation had a much lower laccase activity of 2,430 U l⁻¹, biomass production of 4.5 g l⁻¹, and three laccase isoforms. These results show that P. ostreatus performs much better in submerged fermentation than in solid-state fermentation. This is the first report that shows such atypical behavior in the production of extracellular laccases by fungi.     

Critical importance of moisture content of the medium in alpha-amylase production by Bacillus licheniformis M27 in a solid-state fermentation system

Summary A large reduction (about 30%–78%) is observed in the production of alpha-amylase by Bacillus licheniformis M27 in standardized wheat bran medium under solid-state fermentation when the moisture content of the medium is higher than the standardized value (65%). However, a surge in enzyme production in the first 24 h of fermentation is observed in media with 75% and 85% moisture. The role of decreased oxygen transfer in reducing enzyme tires by about 78% in the medium containing 95% moisture is evident, since the enzyme tire can be effectively increased by agitating the medium during fermentation. No such limitation in oxygen transfer is evident in medium containing 65% moisture even where incubated under static conditions or when the flask is capped by aluminum foil. The data indicate the critical importance of the moisture content of the medium in -amylase production by B. licheniformis M27 in solid-state fermentation systems. The results also have several implications of scientific and techno-economic importance and are useful in explaining some of the advantages of a solid-state fermentation system over the submerged fermentation process. Offprint requests to: B. K. Lonsane     

Biomass estimation of Aspergillus niger growing on real and model supports in solid state fermentation

Summary Direct hydrolysis of Aspergillus niger mycelium growth on amberlite IRA-900 or sugar cane bagasse on solid state fermentation followed by the analysis of soluble protein by the dye binding method was carried out. Hydrolysis with phosphoric acid 0.25M during 7 min allowed maxima protein extraction available to be measured. Color interference of medium components was not observed, allowing the use of this method for biomass estimation when amberlite IRA-900 or sugar cane bagasse are used as support in solid state fermentation processes.     

Solid-state cultivation ofPenicillium capsulatum on beet pulp

Summary Extracellular enzyme production byP. capsulatum during solid-state fermentation on beet pulp is maximal at 30°C with initial moisture contents of 60–75% and when growth medium is supplemented with corn steep liquor, ammonium sulphate and yeast extract. On balance, solid-state co-cultures ofP. capsulatum withT. reesei orT. emersonii do not yield greater overall enzyme activity thanP. capsulatum alone.     

An optimization study of solid-state fermentation: xanthophylls extraction from marigold flowers

Marigold flowers are the main natural source of xanthophylls, and marigold saponified extract is used as an additive in several food and pharmaceutical industries. In this work, the use of a solid-state fermentation (ensilage) process for increasing the yield of xanthophylls extracted from fermented marigold flowers was examined. The process consisted of a mixed culture of three microorganisms (Flavobacterium IIb, Acinetobacter anitratus, and Rhizopus nigricans), part of the normal microbiota associated with the marigold flower. These microorganisms had been previously isolated, and were identified as relevant for the ensilage process due to their capacity to produce cellulolytic enzymes. Based on experimental design strategies, optimum operation values were determined for aeration, moisture, agitation, and marigold-to-inoculum ratio in the proposed solid-state fermentation equipment, leading to a xanthophylls yield of 17.8-g/kg dry weight. The optimum achieved represents a 65% increase with respect to the control. HPLC analysis indicated conservation of extracted oleoresin. Based on the experimental results, interactions were identified that could be associated with the heat and mass-transfer reactions taking place within the bioreactor. The insight gained allows conditions that limit growth and metabolic activity to be avoided.