Chitin-glucan complex production by Komagataella (Pichia) pastoris: impact of cultivation pH and temperature on polymer content and composition

Chitin-glucan complex (CGC) is a valuable biomaterial that can be extracted from the cell wall of several yeast and fungi. In this work, the yeast Komagataella (Pichia) pastoris was grown on glycerol as the sole carbon source in batch cultivation experiments to evaluate the effect of pH (3.5-6.5) and temperature (20-40°C) on CGC production and polymer composition. The CGC content in the biomass and the volumetric productivity (rp) were not significantly affected within the tested pH and temperature ranges. Nevertheless, both parameters could be maximized (CGC ≥ 14 wt% and rp ≥ 3.0 gCGC L−1 day−1) for temperatures within 27-34°C and pH above 6.0 or below 4.0. In contrast, the effect of pH and temperature on the polymer's chitin:β-glucan molar ratio was more pronounced. The highest chitin:β-glucan molar ratio (>14:86) was obtained for the mid-range pH (4.5-5.8) and temperatures (26-33°C), while a drastic reduction of chitin to ≤6%mol was observed outside those ranges. Therefore, a compromise between maximal CGC production and the synthesis of polymers enriched in chitin must be achieved, depending on the final application of this product.