Isoprene Production on Enzymatic Hydrolysate of Peanut Hull Using Different Pretreatment Methods

Abstract

The present study is about the use of peanut hull for isoprene production. In this study, two pretreatment methods, hydrogen peroxide-acetic acid (HPAC) and popping, were employed prior to enzymatic hydrolysis, which could destroy the lignocellulosic structure and accordingly improve the efficiency of enzymatic hydrolysis. It is proven that the isoprene production on enzymatic hydrolysate with HPAC pretreatment is about 1.9-fold higher than that of popping pretreatment. Moreover, through High Performance Liquid Chromatography (HPLC) analysis, the amount and category of inhibitors such as formic acid, acetic acid, and HMF were assayed and were varied in different enzymatic hydrolysates, which may be the reason leading to a decrease in isoprene production during fermentation. To further increase the isoprene yield, the enzymatic hydrolysate of HPAC was detoxified by activated carbon. As a result, using the detoxified enzymatic hydrolysate as the carbon source, the engineered strain YJM21 could accumulate 297.5 mg/L isoprene, which accounted for about 90% of isoprene production by YJM21 fermented on pure glucose (338.6 mg/L). This work is thought to be the first attempt on isoprene production by E. coli using peanut hull as the feedstock. More importantly, it also shows the prospect of peanut hull to be considered as an alternative feedstock for bio-based chemicals or biofuels production due to its easy access and high polysaccharide content.

Pretreatment optimization, process control, mass and energy balances and economics of anaerobic co-digestion of Arachis hypogaea (Peanut) hull and poultry manure

“…The total phenolic contents of the samples were determined using a microtube test (Spectroquant, Merck) closely followed by a 4-aminoantipyrine colorimetric measurement (Monlau et al, 2015). The TS content were determined by drying samples to constant weight at 105°C while for VS, known weights of dried samples were ignited to constant weight at 575 ± 25°C (Wang et al, 2016). Soluble sugars (sucrose and inulin) were extracted using a mild acid hydrolysis protocol after which the anthrone method was used to do further quantification (Dahunsi et al, 2017b).…”

“…In Brazil (South America), an annual production of around 320,000 tons was generated in 2014 also giving more than 90,000 tons of the hulls (Polachini et al, 2016). In China (Asia), annual production is about 13 million tons with approximately 3.64 million tons hulls being generated (USDA, 2014;Wang et al, 2016). In Nigeria (Africa), total production of 8.7 million metric tons was recorded in Nigeria alone in 2011 from a total harvested area of 9.04 million ha (FAOSTAT, 2013).…”

“…The best approach therefore is co-digestions with other energy-yielding substrates as this will enhance substrate synergy and higher microbial diversity leading ultimately to higher biogas yield (Khoufi et al, 2015). Despite the abundance of peanut hulls globally, only few attempts have been documented for its utilization for biofuel generation and such studies focused majorly on ethanol and isoprene productions (Herring and Narayanan, 2016;Polachini et al, 2016;Wang et al, 2016) while its usage for biogas generation is grossly under-reported. Though the potential of the hull for biogas generation in mono-digestion was reported in our recent study (Dahunsi et al, 2017b), the potential synergistic effects in its co-digestion with other substrates in order to improve digestibility and biogas yield is yet to be understood and this was addressed in this research.…”

Mutant Transcriptome Sequencing Provides Insights into Pod Development in Peanut (Arachis hypogaea L.)

“…Thus, as the demand for oil is ever-increasing, there is an urgent need to breed new peanut varieties with high yields, a characteristic that is dependent on pod size. Previous research has shown that pod size is mainly determined by quantitative trait loci (QTL), and several of these have been identified (Fonceka et al, 2012 ; Chen et al, 2016 , 2017 ; Wang et al, 2016 ; Luo et al, 2017 ). Earlier work has shown that peanut genotypes from different backgrounds harbor distinct QTLs; thus, the primary characteristics of peanut which distinguish this plant from others include aerial flowering, a gynophore (peg) that elongates gravitropically, and subterranean fruiting.…”

“…A typical peanut pod is comprised of three parts, a hull, a seed coat (or testa), and an embryo; of these, the hull forms a protective layer surrounding the seed, which itself functions to protect the endosperm and shield the embryo from external stresses. The hull of a peanut is composed of 46.8% holocellulose, 43.4% Klason lignin, 5.8% ash, and 4.0% organic solvent extracts (OSE) (Wang et al, 2016 ).…”