Bioethanol production from microwave-assisted acid or alkali-pretreated agricultural residues of cassava using separate hydrolysis and fermentation (SHF)

Abstract

The effect of microwave (MW)-assisted acid or alkali pretreatment (300 W, 7 min) followed by saccharification with a triple enzyme cocktail (Cellic, Optimash BG and Stargen) with or without detoxification mix on ethanol production from three cassava residues (stems, leaves and peels) by was investigated. Significantly higher fermentable sugar yields (54.58, 47.39 and 64.06 g/L from stems, leaves and peels, respectively) were obtained after 120 h saccharification from MW-assisted alkali-pretreated systems supplemented (D+) with detoxification chemicals (Tween 20 + polyethylene glycol 4000 + sodium borohydride) compared to the non-supplemented (D0) or MW-assisted acid-pretreated systems. The percentage utilization of reducing sugars during fermentation (48 h) was also the highest (91.02, 87.16 and 89.71%, respectively, for stems, leaves and peels) for the MW-assisted alkali-pretreated (D+) systems. HPLC sugar profile indicated that glucose was the predominant monosaccharide in the hydrolysates from this system. Highest ethanol yields (, g/g), fermentation efficiency (%) and volumetric ethanol productivity (g/L/h) of 0.401, 78.49 and 0.449 (stems), 0.397, 77.71 and 0.341 (leaves) and 0.433, 84.65 and 0.518 (peels) were also obtained for this system. The highest ethanol yields (ml/kg dry biomass) of 263, 200 and 303, respectively, for stems, leaves and peels from the MW-assisted alkali pretreatment (D+) indicated that this was the most effective pretreatment for cassava residues.

Comparison of ethanol yield from pretreated lignocellulo-starch biomass under fed-batch SHF or SSF modes

“…The reducing sugar consumption in F-SHF was worked out from the initial sugar concentration in the hydrolysate and the residual sugar concentration in the fermented broth. The other parameters related to ethanol fermentation were computed based on the previous reports ( Barcelos et al., 2011 ; Pereira et al., 2015 ; Yadav et al., 2011 ; Pooja et al., 2018 ) as given under: where Ef is the ethanol concentration (g/L) in fermented broth and W1 is the weight of dry biomass in one litre slurry where 0.82 is the specific gravity of ethanol.…”

The Availability and Assessment of Potential Agricultural Residues for the Regional Development of Second-Generation Bioethanol in Thailand

“…Potential residual biomass from post-harvest and agricultural production processes has been a target of revalorization through ethanol conversion due to its substantial generation rates and the fundamental structure of its saccharide components. Several studies have verified the data on bioethanol conversion from agricultural residues, for example from bagasse, rice husks, cassava peels and oil palm residues [20,[22][23][24]. Despite the properties of lignocellulosic biomass, lignocellulosic ethanol still faces certain constraints when it comes to developing it on an industrial scale [21,25,26].…”

Techno-economic analysis of bioethanol production from microwave pretreated kitchen waste

“…They also confirmed the presence of fermentation inhibitors at high microwave power. Pooja et al [35] accomplished microwave-assisted acid/alkali pretreatment at 300 W for 7 min of agricultural residues of cassava. They suggested that microwave treatment is the most efficient pretreatment method.…”