Screening and Identification of Cold-adapted Fungi with Cellulose Degradation and Its Enzymatic Properties

Objective The aim was to screen strain resources for efficient cellulose degradation and to promote rapid decomposition of straw at low temperature.

Method Low-temperature cellulose degrading fungi were screened by using low-temperature dilution plate coating method, Congo red characterization and quantification of endo-β-glucanase activities. The strains were identified based on morphological characteristics and rDNA-ITS sequence analysis, their enzyme production capacities at different temperatures were investigated, and preliminary studies on the enzymatic properties of crude enzyme extracts were conducted.

Result ① A cold-adapted fungus, namely ZY-50, was obtained and identified as Metapochonia-bulbillosa. There are no reports of cellulase production by this fungus. ② Metapochonia-bulbillosa ZY-50 could grow at low temperatures and has strong cellulase production ability. Its Endo β-glucanase activities were 76.03 U mL⁻¹, 128.34 U mL^−1, and 115.67 U mL⁻¹ at 28℃, 16℃ and 10℃ respectively, and the abilities of the fungus to produce Exo β-glucanase and β-Glucosidase were more stable at 16℃. The highest activities of them were 2.31 U mL⁻¹ and 2.43 U mL⁻¹. The synergistic effect of the three cellulases was stronger at 16℃, with the highest filter paper activity of 7.89 U mL⁻¹. ③ The endo-β-glucanase of the crude enzyme extract had an optimum action temperature of 60℃. The relative enzyme activity was 90% within 1.5 h at temperatures between 10 and 40℃. The optimum pH was 5.0, and its activity was promoted by 10 mmol L⁻¹ Co^{2 +} .

Conclusion Metapochonia-bulbillosa ZY-50 can grow at low temperature and has a strong cellulase production ability, which has a high potential to promote straw decomposition at low temperature.