Solid-state fermentation

Abstract: Solid-state fermentation has emerged as a potential technology for the production of microbial products such as feed, fuel, food, industrial chemicals and pharmaceutical products. Its application in bioprocesses such as bioleaching, biobeneficiation, bioremediation, biopulping, etc. has offered several advantages. Utilisation of agro-industrial residues as substrates in SSF processes provides an alternative avenue and value-addition to these otherwise under- or non-utilised residues. Today with better understanding of biochemical engineering aspects, particularly on mathematical modelling and design of bioreactors (fermenters), it is possible to scale up SSF processes and some designs have been developed for commercialisation. It is hoped that with continuity in current trends, SSF technology would be well developed at par with submerged fermentation technology in times to come.

Abstract: Enzymes are among the most important products. obtained for human needs through microbial sources. A large number of industrial processes in the areas of industrial, environmental and food biotechnology utilize enzymes at some stage or the other. Current developments in biotechnology are yielding new applications for enzymes. Solid state fermentation (SSF) holds tremendous potential for the production of enzymes. Tt can be of special interest in those processes where the crude fermented products may be used directly as enzyme sources. This review focuses on the production of various industrial enzymes by SSF processes. Following a brief discussion of the micro-organisms and the substrates used in SSF systems, and aspects of the design of fermenter and the factors affecting production of enzymes, an illustrative survey is presented on various individual groups of enzymes such as cellulolytic, pectinolytic, ligninolytic, amylolytic and lipolytic enzymes, etc.

Abstract: Despite the increasing number of publications dealing with solid-state (substrate) fermentation (SSF) it is very difficult to draw general conclusion from the data presented This is due to the lack of proper standardisation that would allow objective comparison with other processes Research work has so far focused on the general applicability of SSF for the production of enzymes, metabolites and spores, in that many different solid substrates (agricultural waste) have been combined with many different fungi and the productivity of each fermentation reported On a gram bench-scale SSF appears to be superior to submerged fermentation technology (SmF) in several aspects However, SSF up-scaling, necessary for use on an industrial scale, raises severe engineering problems due to the build-up of temperature, pH, O2, substrate and moisture gradients Hence, most published reviews also focus on progress towards industrial engineering The role of the physiological and genetic properties of the microorganisms used during growth on solid substrates compared with aqueous solutions has so far been all but neglected, despite the fact that it may be the microbiology that makes SSF advantageous against the SmF biotechnology This review will focus on research work allowing comparison of the specific biological particulars of enzyme, metabolite and/or spore production in SSF and in SmF In these respects, SSF appears to possess several biotechnological advantages, though at present on a laboratory scale only, such as higher fermentation productivity, higher end-concentration of products, higher product stability, lower catabolic repression, cultivation of microorganisms specialized for water-insoluble substrates or mixed cultivation of various fungi, and last but not least, lower demand on sterility due to the low water activity used in SSF

Abstract: Abstract Three agricultural residues, wheat straw, wood chips and corn-cob shreds were tested for their ability to adsorb individual dyes and dye mixtures in solutions. Up to 70–75% colour removal was achieved from 500 ppm dye solutions at room temperature using corn-cob shreds and wheat straw. Increasing the temperature had little effect on the adsorption capacity of the residues. The resulting dye-adsorbed residues were found to be suitable substrates for solid-state fermentation (SSF) by two white-rot fungi; Phanerochaete chrysosporium and Coriolus versicolor. Both strains grew uninhibited and produced a maximum protein content of 16, 25 and 35 g and 19, 23 and 50 g in SSF of 100 g dry weight wood chips, corn-cob shreds and wheat straw, respectively, supplemented with ammonical nitrogen to give a C:N ratio of 20:1. This approach provides preliminary results for the remediation of textile effluent and the conversion of agricultural residues into soil conditioner.

Abstract: Solid state fermentation (SSF) has become a very attractive alternative to submerged fermentation (SmF) for specific applications due to the recent improvements in reactor designs. This paper reviews the application of SSF to the production of several metabolites relevant for the food processing industry, centred on flavours, enzymes (α-amylase, fructosyl transferase, lipase, pectinase), organic acids (lactic acid, citric acid) and xanthan gum. In addition, different types of biorreactor for SSF processes have been described.