Optimization of culture conditions for the production and activity of recombinant xylanase from microalgal platform

Abstract

Xylanases are enzymes responsible for the hydrolysis of the heteropolymer xylan. They have wide applications ranging from the bakery, animal husbandry, and textile to pulp and paper industry and biofuel productions. Recombinant xylanase production has been previously reported from different hosts such as bacteria and yeast. Microalgae offer a safe and cost-effective photosynthetic platform for producing recombinant proteins, including therapeutics and industrial enzymes. In this study, we optimized the production of recombinant xylanase expressed and secreted from the green alga, Chlamydomonas reinhardtii. The growth of the culture was optimized using response surface methodology (RSM) based on central composite design (CCD), with two numeric (culture incubation time and agitation rate) and one categoric (light intensity) factors. The optimum biomass concentration was obtained as 0.71 mg/mL from the CCD values. In addition, bubble column photobioreactors were set and compared for the culture growth, the protein concentration, and the enzyme activity under different light intensities and air flows. Increasing the aeration rate from 1 vvm to 2 vvm resulted in improved enzyme activity from 5330.5 U/g to 6277.7 U/g under 3500 lux illumination on the 3rd day of the culture. This study may lead to the further large-scale production of xylanase with high enzyme activity and reveal the advantage of the microalgae as a sustainable platform.