Fermentation of Pretreated High-Biomass Sorghum Hydrolysates to Biohydrogen by Mixed Consortia

In the present study, hydrolysate generated during pretreatment of high-biomass sorghum as a carbon source for biohydrogen production was investigated. The high-biomass sorghum bagasse (HBS) was pretreated using acid (H2SO4) and alkali (NaOH) at various concentrations (0.5–5 % w/v) for the residence time of 30 min at 121 °C, 15 lbs pressure at 10 % (w/v) solid loading. At the optimal acid load of 2 % (w/v) H2SO4 yielded 78.0 g COD/L of hydrolysate. The hydrolysate generated during this pretreatment was analyzed and noticed to contain glucose 10 g L−1, xylose 23 g L−1, arabinose 2.0 g L−1, HMF 1.9 g L−1, furfural 3.5 g−1, acetic acid 9.3 g L−1, formic acid 5.0 g L−1, and phenols 1.9 g L−1. The fermentation studies were conducted in dark conditions using all the hydrolysates by heat-treated mixed microbial consortia. Maximum H2 production rate (HPR), cumulative H2 production (CHP), and specific H2 yield (SHY) were measured. Maximum CHP (328 mL) and SHY (4.68 mol/kg CODr) were registered with acid treatment-resulted hydrolysate, and volatile fatty acid analysis indicated higher acetic acid concentration (1.6 g L−1) showing acidogenic microenvironment directing fermentation toward acetate pathway. The present study assumes importance in safe disposal and simultaneous production of value-added byproducts during lignocellulosic biorefinery. Fermentation of Pretreated High-Biomass Sorghum Hydrolysates to Biohydrogen by Mixed Consortia

Sweet sorghum juice as an alternate substrate for fermentative hydrogen production: Evaluation of influencing parameters using DOE statistical approach

Biohydrogen production using agro-industrial by-products has considerable practical importance. Sweet sorghum is an ideal feedstock for biofuel production in the semi-arid and arid climatic regions. In the present investigation, the juice of SSV 74, a sweet sorghum variety, was examined as a novel substrate for biohydrogen production. The impact of medium pH, substrate, inoculum level and incubation temperature were analyzed at individual and interactive levels on biohydrogen production. Substrate level concentration and pH of the fermentation medium played a critical role on overall biohydrogen production at individual level, and indicated >90 % influence on product yield. On the other hand at interactive level; pH of the fermentation medium, inoculum and substrate concentrations revealed maximum severity index of 78 % (43 % for medium pH vs inoculum concentration and 35 % for inoculum vs substrate concentration). Overall, biohydrogen production yield was enhanced from 283 to 546 mL/3.25 g glucose equivalents of juice upon statistical optimization leading to a >190 % of H2 yield. Along with the H2 production, various acid intermediates were produced with acetate in maximum concentration indicating the occurence of acetogenic fermentatio

Enzymatic hydrolysis of market vegetable waste and subsequent ethanol fermentation-Kinetic evaluation

In this work, kinetic properties evaluation was made for bioethanol production from sugar hydrolysate of vegetable waste. The saccharified sugars were fermented by using Saccharomyces cerevisiae. The effect of various saccharification factors on sugars release were studied and observed that the optimized conditions contributed to 14.4 gL-1of fermentable sugars production. The produced sugars were subjected to batch fermentation by Saccharomyces cerevisiae at pH 4.5 and the kinetic parameters of fermentation were estimated by fitting the experimental data in modified logistic equations. The data revealed product (ethanol) yield (YP/S) of 0.39g/g of reducing sugars. Maximum specific growth rate (μmax), the yield of ethanol on biomass (YP/X) and the yield of biomass on sugars utilization (YX/S) were determined to be 0.18 h-1, 1.097 g/g and 0.313 g/g, respectively. The process yielded 4.13 gL-1 of ethanol by consumption of 10.6 gL-1 sugars with a volumetric production rate of 0.0861±0.002 gL-1 h-1

Xylanase Production by Isolated Fungal Strain, Aspergillus fumigatus RSP-8 (MTCC 12039): Impact of Agro-industrial Material as Substrate

In the present investigation, the imperative role of agro-industrial biomass for improved xylanase production was evaluated using isolated fungal strain. This isolate was identified as Aspergillus fumigatus RSP-8 (MTCC 12039) based on morphological and 18S rRNA ribotyping and the organism was deposited in MTCC, IMTECH Chandigarh with accession number 12039. The isolated fungal strain is mesophilic in nature and produced maximum xylanase at 30 °C, at pH 7 and agitation speed of 150 rpm. Xylanase complex production titers differed with the nature and complexity of carbon source and other physiological growth parameters including aeration, growth temperature, physiological medium pH, initial inoculum levels, etc. Highest xylanase titers (73 U/mL) noticed with hemicellulose isolated from sorghum straw and least with ground nut cake as carbon source among tested agro materials such as rice bran, green gram husk, sorghum straw, groundnut cake and wheat bran. A variation of three fold enzyme titers was observed with different tested carbon sources. Supplementation of glucose as carbon source did not produce any xylanase with this fungal strain revealing the xylanase in this isolate is induced by the carbon source. Variation of hemicellulose concentration as carbon source during the fermentation altered the production xylanase titers. The study suggested that, in xylanase production by A. fumigatus RSP-8, one of the major limiting factors is substrate chemical complexity

Sorghum: A Multipurpose Bioenergy Crop

Bioethanol and biodiesel produced from renewable energy sources are gaining importance in light of volatile fossil fuel prices, depleting oil reserves, and increasing greenhouse effects associated with the use of fossil fuels. Among several alternative renewable energy sources, energy derived from plant biomass is found to be promising and sustainable. Sorghum [Sorghum bicolor (L.) Moench] is a resilient dryland cereal crop with wide adaptation having high water, nutrient, and radiation use efficiencies. This crop is expected to enhance food, feed, fodder, and fuel security. Sweet sorghum is similar to grain sorghum but has the ability to accumulate sugars in the stalks without much reduction in grain production. Hence, it is used as a first-generation biofuel feedstock, where the grain and stalk sugars can be used for producing bioenergy, while energy sorghum or biomass sorghum is increasingly viewed as a potential feedstock for lignocellulosic biofuel production. Although the commercial use of sweet sorghum for bioethanol production has been demonstrated in China and India, the viability of large-scale lignocellulosic conversion of sorghum biomass to biofuels is yet to be demonstrated. This chapter dwells on sorghum feedstock characteristics, biofuel production models, sustainability indicators, and commercialization