Abstract:

As a major global energy consumer, China is confronting the dual severe challenges of fossil fuel dependence and ecological environmental pollution. The development and utilization of renewable clean energy has emerged as a crucial pathway to address this developmental dilemma. In recent years, the conversion of cellulose by functional microorganisms for microbial lipid synthesis, which is regarded as a promising feedstock for biodiesel production, has been recognized as a viable alternative to fossil fuels. In the present study, three functional strains with both lipid-producing and cellulose-degrading capacities were isolated and screened from cow dung, using sodium carboxymethylcellulose (CMC-Na) as the sole carbon source. Their cellulose degradation efficiency, corresponding enzymes activities, lipid accumulation, and taxonomic identity were systematically determined and analyzed. The results demonstrated that all three strains effectively promoted straw degradation. After 5 days of treatment, the straw weight loss rates induced by strains 42, 47a, and 59a were 18.30%, 18.34%, and 18.79%, respectively. The maximum filter paper enzyme activities of these strains were 10.35, 8.84, 3.67 U·mL^-1; the maximum carboxymethyl cellulase activities were 12.78, 14.23, 5.24 U·mL^-1; and the maximum β-glucosidase activities were 4.36, 16.48, 4.45 U·mL^-1, respectively. Notably, the cellulose-to-lipid conversion capacity of all three strains peaked on the 4th day, with lipid contents reaching 34.94%, 69.82%, and 39.25% for strains 42, 47a, and 59a, respectively. Based on 16S rRNA gene sequence analysis, strains 42, 47a, and 59a showed the highest phylogenetic similarity to Calidifontibacillus erzurumensis P2, Bacillus stercoris D7XPN1, and Bacillus safensis NBRC, respectively.

Key words: cellulose degradation, microbial lipids, strain screening, straw resource utilization