Enhanced endoxylanase production by Myceliophthora thermophila with applicability in saccharification of agricultural substrates

Abstract

The production of enzymes by solid-state fermentation is an interesting process and currently used worldwide as it can be carried out in solid matrix in absence of free water. In present study, Myceliophthora thermophila BJTLRMDU3 produced high titres of endoxylanase (890.55 U/g DR, dry residue) using 5 g rice straw at pH 7.0 and at 45 °C with 1:7 (w/v) solid-to-moisture ratio with inoculum rate of 12 × 10 6 spores/ml after 4 days in solid-state fermentation. High enzyme titre was produced after moistening the rice straw with solution containing ammonium sulphate (0.4%), K 2 HPO 4 (1.0%), MgSO 4 •7H 2 O (0.3%), FeSO 4 •7H 2 O (0.03%) and CaCl 2 (0.03%). Addition of sucrose (2% w/v) and ammonium nitrate (2% w/v) further enhanced the endoxylanase production. A high endoxylanase production was achieved at water activity (a W ) of 0.95 (1639.80 U/g DR) that declined drastically below this value. Among different surfactants, Tween 20 (3% v/v) enhanced the secretion of endoxylanase (2047.91 U/g DR). Furthermore, on optimization of K 2 HPO 4 concentration, it was found that 0.5% K 2 HPO 4 improved (2191.28 U/g DR) endoxylanase production and overall 4.35-folds increase in production of endoxylanase was achieved after optimization of culture conditions. The enzyme has potential to liberate monomeric (xylose) as well as oligomeric (xylotiose, xylotetrose, and xylopantose) sugars from xylan. On saccharification of rice straw and corncob with endoxylanase, maximum yield of reducing sugars was 135.61 and 132.61 mg/g of substrate recorded after 48, and 36 h, respectively.

Cellulase production by Myceliophthora thermophila in solid state fermentation and its utility in saccharification of rice straw

“…Similarly, S. thermophile also produced maximum cellulase at a w of 0.95 using combination of wheat straw and cotton oil cake [5] . Similar findings were observed by Dahiya and Singh [19] for high endoxylanase production at a w of 0.95 using rice straw in SSF. Sapna and Singh [15] found maximum phytase at a w of 0.95 by the mould A. oryzae SBS50 in SSF.…”

“…Jain et al [18] reported maximum CMCase of 70.2 U/g at 1:3 moisture ratio using wheat bran in SSF. In contrast, M. thermophila BJTLRMDU3 also supported high endoxylanase production using 1:7 moistening ratio with rice straw as substrate in SSF [19] .…”

The optimization of fermentation conditions for Pichia pastoris GS115 producing recombinant xylanase

“…So, it is necessary to choose cheap nutrients maize meal and bean pulp for fermentation . Therefore, increasing the expression level of xylanase and reducing the cost have become key challenges in xylanase production . Thus, maize meal and bean pulp as cheap nutrients were chosen for the fermentation.…”

“…The high activity of xylanase in the presence of maize meal may be due to the high nutritional content of maize meal, which supports the beginning of microbial growth and replication, and maize meal remains loose even under wet conditions, providing a large surface area for microbial nutrient absorption during SMF. Most studies have found the optimal in carbon, nitrogen, and pH, for the best xylanase activity . Agricultural production is a suitable basic substrate for the economic production of xylanases.…”

Breeding of a thermostable xylanase-producing strain of Myceliophthora thermophila by atmospheric room temperature plasma (ARTP) mutagenesis

“…Thermostable xylanase is a product of numerous thermophilic microorganisms, including Thermomyces lanuginosus ( Wang et al, 2012 ), Thermophilic sporotrichum ( Ghosh et al, 2019 ), Paecilomyces thermophila ( Zhang et al, 2010 ), Myceliophthera thermophila ( Dahiya and Singh, 2019 ), Thermosaccharolyticum ( Jiang et al, 2017 ) and other thermophilic fungi, as well as thermophilic bacteria ( Saleem et al, 2009 ) and thermophilic archaea ( Knapik et al, 2019 ). It has been reported that bacteria can usually produce low molecular weight alkaline xylanase and high molecular weight acid xylanase, while fungi usually produce only high molecular weight acid xylanase.…”