Alcoholic fermentation of thermochemical and biological hydrolysates derived from Miscanthus biomass by Clostridium acetobutylicum ATCC 824

Abstract

This laboratory scale study aims to demonstrate the effectiveness of thermochemical and biological saccharification of Miscanthus giganteus (MG) for generation of fermentable saccharides and its subsequent fermentation into solvents i.e. acetone, ethanol and butanol (ABE) using Clostridium acetobutylicum ATCC 824. Saccharide hydrolysates were derived from MG by thermochemical (water, acid and alkali at 130 o C) and biological saccharification (Fibrobacter succinogenes S85) processes and were subjected to batch fermentation for 120 hours using C. acetobutylicum ATCC 824. At the end of fermentation of thermochemically-derived hydrolysates, 742 g m -3 of saccharides from water treatment, 9572 g m -3 of saccharides from acid treatment and g m -3 of saccharides from alkali treatment were fermented and yielded 0.045, 0.0069 and 0.01 g g -1 of total solvents, respectively. Similarly, at the end of fermentation of biological hydrolysate (using F. succinogenes), 2504 g m -3 of saccharides was fermented and yielded 0.091 g g -1 of total solvents. The highest yield of total solvents was achieved by water (thermochemical) and biological saccharification of MG using C. acetobutylicum. Whereas, acid and alkali-treated hydrolysates showed lower yields of solvents presumably due to production of inhibitory compounds during saccharification. Compared to thermochemical saccharification, biological saccharification using F. succinogenes is a promising approach since it yielded the highest amount of solvents whilst being eco-friendly. Our future studies will focus on optimisation of biological saccharification (using F. succinogenes) and sequential co-culture fermentation (using C. acetobutylicum). The development of alternative consolidated bioprocessing approach using biological saccharification will contribute towards making lignocellulosic biofuels a reality.

Energy plants as biofuel source and as accumulators of heavy metals

“…Furthermore, instead of ethanol, products of fermentation can be isobutanol if fermentation is performed with Clostridium sp. Compared to ethanol, isobutanol has a higher energy density, and low absorption of moisture from the air, therefore it is less corrosive [34][35][36]. As the pretreatment thermochemical saccharification by H 2 SO 4 or NaOH was used.…”

Advances and Applications of Clostridium Co-culture Systems in Biotechnology

“…Firstly, co-culturing Clostridium spp. and other microorganisms makes it possible to utilize more extensive and complex substrates including the abundant renewable resources of lignocellulosic biomass in nature such as cedar ( Rabemanolontsoa et al, 2016 ), aspen ( Xu and Tschirner, 2014 ), agave ( Oliva-Rodríguez et al, 2019 ), cassava ( Qi et al, 2018 ), miscanthus biomass ( Raut et al, 2019 ), switchgrass ( Flythe et al, 2015 ), salix ( Pang et al, 2018b ), and many types of agricultural waste such as crop straw, fruit residue, etc. Food waste ( Tavabe et al, 2010 ) and industrial waste including biodiesel waste (crude glycerol) and yeast waste can also be used.…”

“…Raut utilized Fibrobacter succinogenes S85 with highly efficient saccharification ability found in the herbivore rumen, co-cultured with C. acetobutylicum ATCC824, and achieved a yield of 0.091 g/g total solvents from miscanthus biomass. This provides a promising approach using biological saccharification to make lignocellulosic bio-fuels ( Raut et al, 2019 ). In addition, co-culture of solventogenic Clostridia and other bacteria can also produce lactic acid ( Ndaba et al, 2015 ), butyric acid, and caproic acid.…”

“…In most cases, the co-culture medium contained growth factors necessary for the normal growth and metabolism of the two bacteria, or metal ions, trace elements and vitamins etc., in addition to different substrates, to maintain the stability of the co-culture and the performance of the fermented products ( Ding et al, 2009 ). Recently, the method of mixing components of the medium at different proportions and selecting the best mixing ratio according to the fermentation performance was also used to optimize the medium, which is mainly explored in new co-cultures ( Xia et al, 2017 ; Raut et al, 2019 ).…”