Effects of Pretreatment of Single and Mixed Lignocellulosic Substrates on Production of Endoglucanase by Bacillus aerius S5.2

Abstract

A mixed substrate (MS) comprising oil palm empty fruit bunch (EFB), oil palm frond (OPF), and rice husk (RH) was evaluated for endoglucanase production by Bacillus aerius S5.2. Effects of sulphuric acid, sodium hydroxide, N-methylmorpholine-N-oxide (NMMO), and hydrothermal pretreatments on endoglucanase production were investigated. Endoglucanase production by B. aerius on the untreated (0.677 U/mL) and pretreated MS (0.305 -0.630 U/mL) was generally similar, except that the acid (0.305 U/mL) and hydrothermal (0.549 U/mL) pretreatments that were more severe consequently produced significantly lower titres. Alkali pretreatment supported the highest enzyme production (0.630 U/mL) among all pretreatments that were studied. When endoglucanase production on the alkali-pretreated MS and single substrates (SS) was compared, alkali-pretreated EFB produced a titre (0.655 U/mL) similar to the MS, and this was significantly higher than titres recorded on OPF (0.504 U/mL) and RH (0.525 U/mL). Lower enzyme production was found to be consistent with higher pretreatment severity and greater removal of amorphous regions in all the pretreatments. Furthermore, combining the SS showed no adverse effects on endoglucanase production.

Thermotolerant glycosyl hydrolases-producing Bacillus aerius CMCPS1 and its saccharification efficiency on HCR-laccase (LccH)-pretreated corncob biomass

“…Previously, a variety of microorganisms belonging to the genera Bacillus, Geobacillus, Thermotoga, Caldibacillus, Acidothermus, Caldocellum, and Clostridium were reported to produce thermostable cellulases [2]. Furthermore, an enhanced endoglucanase production by Bacillus aerius S52 on mixed lignocellulosic substrates was attempted [20]. However, there exist no previous reports of thermophilic B. aerius producing the thermotolerant cellulase, as the majority were reported in B. licheniformis and B. subtilis [2,21].…”

Impact of pretreatment severity on fungal cellulase production on sugarcane bagasse substrate

“…Higher amount of lignin in pretreated solids may be unfavourable for cellulase production in many microorganisms [30,31]. Oke et al [12] also reported lower endoglucanase production on hydrothermal pretreated combined substrates compared to the NaOH-treated one. Thus, NaOH was selected as the preferred pretreatment method for the rest of the study.…”

“…This observation agrees with some previous studies, which suggested that extremes of pretreatment severity could be detrimental to cellulase biosynthesis in different microorganisms. The study by Oke et al [12] found that substrates pretreated with harsher treatments had lower enzyme production than those with milder treatments. They attributed this to the degradation of amorphous regions in the substrates because of the severe pretreatments.…”

“…This has led to a lack of clarity regarding how pretreatment severity affects cellulase production. While some studies suggested that severe pretreatment is detrimental to cellulase production [12,13], others have claimed that it favours high enzyme titres [14,15]. One reason for this disparity is that different types of substrates and pretreatment methods are often compared with each other, thereby introducing several confounding factors from the widely varying substrate characteristics.…”

Optimization of Carboxymethyl cellulase production by Bacillus sp. NAB37 and biocatalytic potential in saccharification of acid-alkali pretreated Parthenium hysterophorus

“…As a consequence, the titers of the free cellulases are low due to adsorption of the produced cellulases over the biomass particles. Oke et al [21] have seen maximum endoglucanases synthesis by Bacillus aerius S5.2 using untreated lignocellulose.…”