Construction of a recombinant Trichoderma reesei strain expressing Aspergillus aculeatus β‐glucosidase 1 for efficient biomass conversion

Abstract

To develop a Trichoderma reesei strain appropriate for the saccharification of pretreated cellulosic biomass, a recombinant T. reesei strain, X3AB1, was constructed that expressed an Aspergillus aculeatus β-glucosidase 1 with high specific activity under the control of the xyn3 promoter. The culture supernatant from T. reesei X3AB1 grown on 1% Avicel as a carbon source had 63- and 25-fold higher β-glucosidase activity against cellobiose compared to that of the parent strain PC-3-7 and that of the T. reesei recombinant strain expressing an endogenous β-glucosidase I, respectively. Further, the xylanase activity was 30% lower than that of PC-3-7 due to the absence of xyn3. X3AB1 grown on 1% Avicel-0.5% xylan medium produced 2.3- and 3.3-fold more xylanase and β-xylosidase, respectively, than X3AB1 grown on 1% Avicel. The supernatant from X3AB1 grown on Avicel and xylan saccharified NaOH-pretreated rice straw efficiently at a low enzyme dose, indicating that the strain has good potential for use in cellulosic biomass conversion processes.

Identification of Major Facilitator Transporters Involved in Cellulase Production during Lactose Culture ofTrichoderma reeseiPC-3-7

“…Over a 144 h time course, aliquots (10 mL) were sampled every 12 h. Residual sugar was measured in the supernatants collected by filtration, and mycelial mass was measured after drying at 55 C for 48 h. To facilitate comparison to previous data, cellulase production experiments were also performed by inoculating 10 7 spores of the PC-3-7, the PCÁ77, and the PCÁ79 strain into 50 mL of basal medium containing 1% cellulose (Avicel, Funakoshi Pharmaceutical, Tokyo, Japan), 1% cellobiose, or 30 mM lactose as sole carbon source, and cultivated for 6 d at 28 C in a shaker at 220 rpm.…”

“…26) Due to its high cellulase productivity, PC-3-7 is also used industrially to enhance lignocellulosic biomass y To whom correspondence should be addressed. Tel: +81-258-47-9407; Fax: +81-258-47-9400; E-mail: owataru@vos.nagaokaut.ac.jp conversion 28,29) and to reduce the cost of saccharification. Because several PC-3-7 derivative strains are being used industrially, the next focus of our research is optimization of strain cultivation parameters in order to improve cellulase production further.…”

Optimization of Medium Components for β-glucosidase Production in Schizophyllum commune KUC9397 and Enzymatic Hydrolysis of Lignocellulosic Biomass

“…BGL converts the oligosaccharides produced by EG and CBH into glucose (Kawai et al 2013). Low BGL activity leads to cellobiose accumulation and reduced biomass conversion efficiency (Nakazawa et al 2012). BGL derived from S. commune KUC9397 therefore played a crucial role in glucose production from cellulose.…”

Newly isolated Penicillium oxalicum A592-4B secretes enzymes that degrade milled rice straw with high efficiency

“…38,39) To compensate for these drawbacks, β-glucosidase genes of Aspergillus aculeatus are introduced and expressed to enhance the β-glucosidase activity and to increase the saccharification rate of alkali-treated rice straw. 40) A. cellulolyticus is a strain with high cellulose degradation capability and was predicted as a promising strain for a single application because its cellulase showed higher β-glucosidase activity than that of T. reesei. In fact, the cellulase of A. cellulolyticus was much more active than that of T. reesei on substrates consisting of uniform cellulose, such as cellulose powder.…”

“…44) It is a well-known approach to compensate for insufficient degradation activities by introducing available enzyme genes of different origins, and has been adopted by many researchers, including Nakazawa et al 40) The newly isolated secreted enzymes of P. oxalicum show a higher degradation activity on milled rice straw than CTec2. This is considered the first case for enzymes originating from a single strain that is not genetically modified.…”