Improved xylanase production by Trichoderma reesei grown on L-arabinose and lactose or D-glucose mixtures

Trichoderma reesei Rut C-30 was grown on eight different natural or rare aldopentoses as the main carbon source and on mixtures of an aldopentose with D-glucose or lactose. The fungal cells consumed all aldopentoses tested, except L-xylose and L-ribose. The highest total xylanase and cellulase activities were achieved when cells were grown on L-arabinose as the main carbon source. The total xylanase activity produced by cells grown on L-arabinose was even higher than that produced by cells grown on an equal amount of lactose. In co-metabolism of D-glucose (15 g l(-1)) and L-arabinose (5 g l(-1)), the total volumetric and specific xylanase productivities were improved (derepressed) approximately 23- and 18-fold, respectively, compared to a cultivation on only D-glucose (20 g l(-1)). In a similar experiment, in which cells were grown on a mixture of lactose and L-arabinose, the xylanase productivity was approximately doubled, compared to a cultivation on only lactose. The cellulase productivities, however, were not improved by the addition of L-arabinose. Compared with a typical industrial fungal enzyme production process with lactose as the main carbon source, better volumetric and specific xylanase productivities were achieved both on a lactose/arabinose mixture and on a glucose/arabinose mixture.