Subcritical water (SCW) treatment has gained enormous attention as an environmentally friendly technique for organic matter and an attractive reaction medium for a variety of applications. In the current work the process parameters were optimized by RSM model.
Conversion of lignocellulosic biomass into monomeric carbohydrates is economically beneficial and suitable for sustainable production of biofuels. Hydrolysis of lignocellulosic biomass using high acid concentration results in decomposition of sugars into fermentative inhibitors. Thus, the main aim of this work was to investigate the optimum hydrolysis conditions for sorghum brown midrib IS11861 biomass to maximize the pentose sugars yield with minimized levels of fermentative inhibitors at low acid concentrations. Process parameters investigated include sulfuric acid concentration (0.2-1 M), reaction time (30-120 min) and temperature (80-121°C). At the optimum condition (0.2 M sulfuric acid, 121°C and 120 min), 97.6% of hemicellulose was converted into xylobiose (18.02 mg/g), xylose (225.2 mg/g), arabinose (20.2 mg/g) with low concentration of furfural (4.6 mg/g). Furthermore, the process parameters were statistically optimized using response surface methodology based on central composite design. Due to the presence of low concentration of fermentative inhibitors, 78.6 and 82.8% of theoretical ethanol yield were attained during the fermentation of non-detoxified and detoxified hydrolyzates, respectively, using Pichia stipitis 3498 wild strain, in a techno-economical way.
The present work investigates the
efficiency of two pretreatment
pathways of biomass, namely ionic liquid (IL) and dilute sulfuric
acid (H2SO4) hydrolysis. Both processes are
compared in terms of their composition and enzymatic saccharification
efficacy. For the IL process, bamboo was dissolved in 1-ethyl-3-methylimidazolium
acetate ([Emim][OAc]) at different temperatures (90, 110, 130, and
150 °C) for 3 h. These pretreated bamboo samples were then characterized
by thermogravimetric analysis and X-ray diffraction to evaluate the
biomass crystallinity and thermal decomposition temperature. The crystallinity
index, thermal decomposition temperature, hemicellulose, and lignin
content of bamboo were found to decrease after [Emim][OAc] pretreatment.
Further, the IL pretreated biomass significantly enhanced the enzymatic
saccharification of cellulose component of bamboo. The enzymatic hydrolysis
rate for IL pretreated biomass was 4.7 times higher than that of the
acid pretreated biomass. This was primarily attributed to the difference
in the crystallinity and delignification in the IL process. To improve
the enzymatic hydrolysis efficiency of bamboo, a combined pretreatment
(dilute acid + ionic liquid) process was also employed and compared
with IL pretreated cellulose and bamboo samples. The consequences
of this investigation revealed that IL pretreatment may offer novel
favorable circumstances compared to a dilute acid pretreatment process
for bamboo which can deliver high sugar yields with IL pretreatment.
This work was aimed at investigating the effect of process parameters on dilute acid pretreatment and enzymatic hydrolysis of spent citronella biomass (after citronella oil extraction) and sugarcane bagasse on total reducing sugar (TRS) yield. In acid pretreatment, the parameters studied were acid concentration, temperature, and time. At the optimized condition (0.1 M H2SO4, 120°C, and 120 min), maximum TRS obtained was 452.27 mg·g−1and 487.50 mg·g−1for bagasse and citronella, respectively. Enzymatic hydrolysis of the pretreated biomass usingTrichoderma reesei26291 showed maximum TRS yield of 226.99 mg·g−1for citronella and 282.85 mg·g−1for bagasse at 10 FPU, 50°C, and 48 hr. The maximum crystallinity index (CI) of bagasse and citronella after acid pretreatment obtained from X-ray diffraction analysis was 64.41% and 56.18%, respectively. Decreased CI after enzymatic hydrolysis process to 37.28% and 34.16% for bagasse and citronella, respectively, revealed effective conversion of crystalline cellulose to glucose. SEM analysis of the untreated and treated biomass revealed significant hydrolysis of holocellulose and disruption of lignin.
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