Experimental study on ethanol production from hydrothermal pretreated rapeseed straw by simultaneous saccharification and fermentation

Abstract

BACKGROUND: Rapeseed straw is an agricultural residue increasingly produced in recent years due to a growing interest in biodiesel production. In the present study, rapeseed straw pretreated by liquid hot water was tested as a substrate to optimize ethanol production by simultaneous saccharification and fermentation (SSF). Temperature, time, substrate loading and cellulase charge were selected as operation variables and modified according to a three-level four-variable experimental design. Ethanol concentration, ethanol yield and volumetric productivity were monitored and adjusted to a quadratic model using response surface methodology. RESULTS: Optimal SSF conditions, based on the mathematical model in terms of ethanol yield and concentration, were found to be 40 • C, 71 h, 10% substrate loading, and 40 FPU g −1 substrate. The resulting ethanol concentration was 23 g L −1 , which corresponds to 69% ethanol yield. CONCLUSION: Liquid hot water is an effective pretreatment that increased the cellulose concentration of rapeseed straw, making it a good substrate for SSF, with a maximum yield of 0.12 g ethanol g -1 dry straw. The novel combination of hydrothermal pretreatment and SSF configuration results in yields comparable yields with those previously reported, and has additional advantages, e.g. no chemicals use and high solid concentration operation.

Hemicellulose-derived sugars solubilisation of rape straw. Cofermentation of pentoses and hexoses by Escherichia coli

“…Finally, the raw material was stored in dry and dark conditions until its use. As indicated in a previous work (López-Linares et al, 2014) the chemical composition of milled rape straw was (dry weight): 39.1 ± 0.9% glucose, 20.9 ± 1.0% xylose, 2.4 ± 0.3% galactose, 1.1 ± 0.2% arabinose, 1.3 ± 0.1% mannose, 16.8 ± 0.6% lignin, 2.6 ± 0.3% acetyl groups, 5.3 ± 0.5% ash and 13.1 ± 0.8% extractives. Ethanol from rape straw hemicelluloses…”

“…However, several researches have been carried out engineering of bacterial pathways to generate E. coli strains able to achieve higher ethanol yields (Fernández-Sandoval et al, 2012). Different genetically engineered E. coli strains have been used to ferment hydrolysates from corn stover (Jin et al, 2012), Eucalyptus (Castro et al, 2014), sugarcane bagasse (Geddes et al, 2011) or wheat straw (Saha et al, 2011) yielding higher ethanol productions and showing more resistance to toxic compounds than traditional ethanologenic microorganisms.…”

Effect of Cellulase, Substrate Concentrations, and Configuration Processes on Cellulosic Ethanol Production from Pretreated Arundo donax

“…Moreover, according to Hoyer et al (2009) andLópez-Linares et al (2014a), the use of higher pretreated biomass loadings (up to 10%) resulted in a higher ethanol concentration and, at same time, no significant decrease in the cellulose conversion occurred. These results confirmed that there was no end-product accumulation during the SSF process when using a less than 10% biomass concentration, which was the limit to obtain good cellulose conversion (Olofsson et al 2008).…”

Rapeseed straw as a renewable source of hemicelluloses: Extraction, characterization and film formation

“…The rapeseed woody stem has a diameter of 1-4 cm and a height of 1.5 m. The stem is not suitable for cattle feed but is left in the field as nutrients after harvest. Research on oil-rapeseed straw valorization has so far only focused on fuel applications (Ryden et al, 2014;Wood et al, 2014;Mathew, Chaney, Crook, & Humphries, 2011a;Mathew, Chaney, Crook, & Humphries, 2011b;Lu, Zhang, & Angelidaki, 2009;López-Linares et al, 2014;Lu, Zhang, & Angelidaki, 2011;Jeong, Um, Kim, & Oh, 2010). Oil rapeseed has many important applications, and in the interest of applying the biorefinery concept, it will be important to find valueadded applications of the straw, which is currently considered a waste.…”