Solid state fermentation (SSF) refers to the microbial fermentation, which takes place in the absence or near absence of free water, thus being close to the natural environment to which the selected micro organisms, especially fungi, are naturally adapted. SSF has been used in the world for a long time. This technology is commonly known in the East, for traditional manufacture of fermented foods, and in the west, for mould-ripened cheese. It can be defined as a system, in which the growth of selected microorganism(s) occurs on solid materials with low moisture contents and has been identified as a potentially important methodology and technique in biotechnology. Nowadays, SSF is an economically viable, practically acceptable technology for large-scale bioconversion and biodegradation processes. Development of sustainable SSF and bioprocess technology is an emerging, multidisciplinary field with possible application to the production of enzymes, chemicals, bioethanol and pharmaceuticals. SSF offers many advantages over conventional submerged fermentation (SMF) such as, simple and inexpensive substrates, elimination of the need for solubilisation of nutrient from within solid substrates, elimination of the need for rigorous control of many parameters during fermentation, product yields are mostly higher, lower energy requirements, produce less waste water, no foam generation and relatively easy recovery of end products. SSF provides flexibility in terms of the raw materials to be used and their capability to produce various value-added products.

https://medcraveonline.com/JABB/JABB-04-00094.pdf

Design aspects of solid state fermentation as applied to microbial bioprocessing

Advances in solid-state fermentation for bioconversion of agricultural wastes to value-added products: Opportunities and challenges.

Advances in solid-state fermentation for bioconversion of agricultural wastes to value-added products: Opportunities and challenges

Bioreactors in solid state fermentation technology: Design, applications and engineering aspects.

Sorghum is an important crop that serve multiple purposes as human food, animal feed, and bioenergy production. There are opportunities to produce different types of biofuels from sorghum-based biomass. Sorghum with its vast genetic resources can serve as bioenergy crop and not compete against the value of it as food and nutritional security crop. Bioenegy crops provides an opportunity for agriculture to be part of solution for energy and mitigation to climate change. This review provides detailed overview and current knowledge on the conversion of sorghum biomass (stalks, leaves, and grains) into liquid (bioethanol, biodiesel, and bio-oil), gas (biohydrogen, biogas, and syngas) and solid (biochar) biofuels. Progress made in the different sorghum-based biomass pretreatment and conversion processes including chemical, biochemical, thermochemical and biological processes (e.g. saccharification, fermentation, transesterification, hydrothermal liquefaction, pyrolysis, and gasification) are highlighted and described. In addition, several value-added products from sorghum gaining importance in biofuels production are summarized. Finally, the potential outlook on sorghum based biorefiners and potential for improving sorghum-based biofuel production is presented and discussed. The biorefinery concept offers a considerable scope for optimization of sorghum biomass utilization to produce biofuels and biochemicals. However, there is further need to clearly identify the best methods of pre-treatment, processing, and products from different sources. Sorghum with its high biomass production and multiple use has the potential to be key biofuel crop. Further research is needed to identify most efficient and cost effective processes to ensure the value of biofuel and other bioproducts from sorghum. A complete lifecycle analyses indicating the challenges and opportunities to enhance the efficiency, benefits, and challenges in different steps and finding solutions to overcome those challenges will be of prime importance. Strong collaboration between private and public sector researhcers and multidisciplinary teams will be required to develop a comprehensive biorefinery models.

Production of biofuels from sorghum

Xylanases encompass a broad spectrum of industrial applications like food, animal feed, textile and biofuel. This study aimed at optimization of solid-state fermentation by Aspergillus niger CCUG33991 for maximum xylanase production using low-cost agro-industrial residues 1 in tray bioreactor. SSF 2 was performed using wheat bran, sorghum stover, corn cob and soybean meal in flasks for investigation of appropriate substrate, initial pH, media composition and minerals solution. Thereafter, the obtained results combined with results of earlier experiments were used for exploring the effects of particle size, initial moisture content and temperature in tray bioreactor. OFAT method 3 was followed to select optimum level of each parameter. Next, effect of air-drying and pelleting condition were tested on enzyme stability. Finally, the extracted enzymes were subjected to zymography. The highest xylanase activity of 2919±174 U/g-IDW 4 at 48 h was achieved using wheat bran with particle size range of 0.3–0.6 mm, initial moisture level of 70%, moistened by distilled water containing 1% (v/v) glycerol and 1% (w/v) of (NH4)2SO4, and controlled bed temperature in the range of 28–35 °C with surface aeration. As a result, a 2.5-fold higher and 24 h faster xylanase production in trays than in flasks was attained. The enzyme also showed a great deal of stability to air-drying and pelleting condition. Zymogram analysis confirmed multiple isoforms of xylanase. SSF in tray bioreactor is a potential method for xylanase production. Wheat bran as low-cost, time-saving and xylan-containing hemicellulosic agro-waste is preferable to use as the carbon and energy sources for maximum production of xylanase.

Mokhtar Miranzadeh

Papers

Bioprocessing of agro-industrial residues for optimization of xylanase production by solid- state fermentation in flask and tray bioreactor

Bed moisture estimation by monitoring of air stream temperature rise in packed-bed solid-state fermentation