The potential of degrading natural chitinous wastes to oligosaccharides by chitinolytic enzymes from two Talaromyces sp. isolated from rotten insects ( Hermetia illucens ) under solid state fermentation

It is difficult to produce chitin oligosaccharides by hydrolyzing untreated natural chitinous waste directly. In this study, two fungi Talaromyces allahabadensis Hi-4 and Talaromyces funiculosus Hi-5 from rotten black soldier fly were isolated and identified through multigene phylogenetic and morphological analyses. The chitinolytic enzymes were produced by solid state fermentation, and the growth conditions were optimized by combining single-factor and central composite design. The best carbon sources were powder of molting of mealworms (MMP) and there was no need for additional nitrogen sources in two fungi, then the maximum chitinolytic enzyme production of 46.80 ± 3.30 (Hi-4) and 55.07 ± 2.48 (Hi-5) U/gds were achieved after analyzing the 3D response surface plots. Pure chitin (colloidal chitin) and natural chitinous substrates (represented by MMP) were used to optimize degradation abilities by crude enzymes obtained from the two fungi. The optimum temperature for hydrolyzing MMP (40 °C both in two fungi) were lower and closer to room temperature than colloidal chitin (55 °C for Hi-4 and 45 °C for Hi-5). Then colloidal chitin, MMP and the powder of shrimp shells (SSP) were used for analyzing the products after 5-day degradation. The amounts of chitin oligosaccharides from SSP and MMP were about 1/6 (Hi-4), 1/17 (Hi-5) and 1/8 (Hi-4), 1/10 (Hi-5), respectively, in comparison to colloidal chitin. The main components of the products were GlcNAc for colloidal chitin, (GlcNAc) 2 for MMP, and oligosaccharides with higher degree of polymerization (4–6) were obtained when hydrolyzing SSP, which is significant for applications in medicine and health products.