Xylanase production from a new strain of Aspergillus terreus S9 and its application for saccharification of rice straw using combinatorial approach

Abstract

High production cost and lack of process‐suitable characteristics in available microbial xylanases limit their vast industrial application potential. A new strain of Aspergillus terreus S9 isolated from mushroom compost (Directorate of Mushroom Research, Solan, India), utilized agro‐industrial wastes as substrates for growth, and produced a process‐apt xylanase. The study is the first ever report of a thermostable (60–90°C) and broad range pH stable (6.0–10.0) xylanase from a strain of Aspergillus terreus. Of a total of ten process variables examined based on Plackett‐Burman design, four variables, i.e., wheat bran, incubation time, pH, and CaCl2 were earmarked to have substantial influence on xylanase production. These selected four variables were further optimized using Design of Experiments (DoE) approach (response surface methodology), and xylanase yield was enhanced (1.92‐fold). Saccharification potential of xylanase was assessed using rice straw as substrate, under several sets of combinatorial regimes. Results showed that alkali pretreatment (0.2M KOH) followed by acid pretreatment (1% sulphuric acid) and enzymatic hydrolysis with cellulase and xylanase yielded maximum sugars. Desired industrial traits of A. terreus S9 xylanase reflect its application prospective for valorization of lignocellulosic biomass for production of biofuel‐ethanol/other industrial products. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1210–1219, 2018

Bioprocess development for production of a process-apt xylanase with multifaceted application potential for a range of industrial processes

“…Sorghum straw was earmarked as a good substrate for SSF based production of xylanase from A. tubingensis FDHN1 [1]. Sharma and Bajaj [28] screened a total of ten process variables based on Plackett-Burman design, and reported that four variables, i.e. wheat bran, incubation time, pH, and CaCl 2 were the most effective ones for xylanase production from A. terreus S9 under SmF.…”

“…particle size (mm), liquid to solid ratio (w/v), and avicel (g) resulted in two-fold increase in cellulase production from Penicillium oxalicum EU2106 under SSF [33]. Optimization of variables like wheat bran, incubation time, pH, and CaCl 2 using response surface methodology resulted in 1.92-fold increased xylanase yield from A. terreus S9 under SmF [28]. Similarly, process variables like temperature, initial moisture content, and inoculum (log number of spores), were optimized using a Box-Behnken design for xylanase production from Aspergillus niger under SSF on spent coffee waste to achieve 1.39-fold increased yield [23].…”

“…Xylanases due to their vast application potential in various industries such as food, feed, dairy, bakery, pulp and paper, biofuel, among others, have become the focus of intense research [22,28,29,32]. Considering the hostile industrial process conditions like extremes of pH, elevated temperature, and presence of various enzyme inhibitors, the xylanases intended for process applications must be robust enough to withstand such an environment [8,29].…”

“…High production cost is one of the major bottlenecks that limits the wide range industrial application of xylanases. Considering that substrates/medium components constitute the major chunk of enzyme production cost, usage of low-cost agro-industrial residues as substrates to support the growth of process organism may help lowering down the enzyme production cost [28,29]. Additionally, valorization of agro-industrial residues may offer distinctive economic, environmental, and strategic advantages [28].…”

“…Considering that substrates/medium components constitute the major chunk of enzyme production cost, usage of low-cost agro-industrial residues as substrates to support the growth of process organism may help lowering down the enzyme production cost [28,29]. Additionally, valorization of agro-industrial residues may offer distinctive economic, environmental, and strategic advantages [28]. Although submerged fermentation (SmF) has widely been used for microbial enzyme production, the solid state fermentation (SSF) has gained substantive interest due to its advantages [20], such as simplicity of media, machinery, control system, downstream processing or process scale-up, lower capital/operational cost, and energy and space requirement, increased enzyme yield, among others [4,12,14,31].…”