Hydrolytic pre-treatment methods for enhanced biobutanol production from agro-industrial wastes

Abstract

Brewery industry liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry wastewater (SIW) have been considered as substrates to produce biobutanol. Efficiency of hydrolysis techniques tested to produce fermentable sugars depended on nature of agro-industrial wastes and process conditions. Acid-catalysed hydrolysis of BLW and BSG gave a total reducing sugar yield of 0.433 g/g and 0.468 g/g respectively. Reducing sugar yield from microwave assisted hydrothermal method was 0.404 g/g from APS and 0.631 g/g from APUS, and, 0.359 g/g from microwave assisted acid-catalysed SIW dry mass. Parameter optimization (time, pH and substrate concentration) for acid-catalysed BLW hydrolysate utilization using central composite model technique produced 307.9 g/kg glucose with generation of inhibitors (5-hydroxymethyl furfural (20 g/kg), furfural (1.6 g/kg), levulinic acid (9.3 g/kg) and total phenolic compound (0.567 g/kg)). 10.62 g/L of acetone-butanol-ethanol was produced by subsequent clostridial fermentation of the substrate.

Biological and Chemical Strategies for the Treatment of Sugar Industry Effluents

“…Sugar industries release a variety of contaminants which are toxic for the environment (Ahmad et al, 1982;Samuel et al, 2011;Tanksali, 2013). Relevant literature (Aguilara et al, 2018;Gopinath et al, 2018;Jayabalan et al, 2019;Maitia et al, 2018;Prasad et al, 2015;Sahu, 2019;Tiwari et al, 2017) for the treatment of sugar industry effluents by chemical and biological methods has been consulted. The treatment procedures by the construction of microbial fuel cell, microbial electrolytic cell (Jayabalan et al, 2019), electro-chemical oxidation (Sahu, 2019), valorization (Gopinath et al, 2018), biological synthesis of silver nanoparticles (Aguilara et al, 2018), electro-oxidation collective technique (Tiwari et al, 2017) and hydrolytic pretreatment for the manufacture of enriched biobutanol (Maitia et al, 2018) were also reviewed.…”

“…The reaction parameters (concentration of substrate, pH and time) were optimized by using central composite model technique for acid-catalysed BLW hydrolysis. This optimization resulted in generation of inhibitors including acetone-butanolethanol (10.62 g/L), total phenolic compounds (0.567 g/kg), levulinic acid (9.3 g/kg), furfural (1.6 g/kg), 5-hydroxymethyl furfural (20 g/kg) (Maitia et al, 2018).…”

Study of Carbohydrate Hydrolysis From Arracacha Roots (Arracacia Xanthorriza Bancroft) to Produce Fermentable Sugars

“…This result is associated with presence of acetyl groups by deacetylation of hemicelluloses during the pretreatment. These are not degraded despite the prolonged storage time, and they were possibly entirely hydrolyzed to form acetic acid by the action of the acid environment in which the pretreatment was carried out (Maiti et al, 2018), regardless of the residence time at which it was submitted.…”

“…There was also an effect (0,28 ± 0,002 mgEF/mL) of H 2 SO 4 concentration, temperature, and residence time in the formation of the environment that fosters pentose dehydration, until their degradation to furfural in pre-treated starchy waste. This could be explained by the way in which many monomeric sugars (pentoses) were possibly hydrolyzed during the process of acid pretreatment in AR; these sugars would be degraded to this inhibiting compound (furfural) (Maiti et al, 2018). Lastly, AR have phenolic compounds within their structure, which act well as major enzymes and microbial inhibitors.…”

“…Chemical pretreatments have the presence of inhibitors in each of the mentioned stages (Zabed et al, 2017), which causes the delay of yeast activity and an extension of fermentation time. Due to hydrolytic pretreatments applied to vegetable material (like furfural, hydroxymethylfurfural, and acetic acid, among other compounds) (Maiti et al, 2018) it has a major negative effect on enzymes (Wojtusik, Villar, Zurita, Ladero, and Garcia-Ochoa, 2017).…”