Construction and Application of Low Cellulase-producing Bacillus licheniformis Strains for Bio-pulping of Bamboo
Xue, Le | Han, Haihong | Fan, Han | Li, Piwu | Wang, Tengfei | Xiao, Jing | Wang, Ruiming | Wang, Junqing
To prevent cellulose loss during bio-pulping, two cellulase genes in Bacillus licheniformis 20085 were knocked out by homologous exchange technique. An engineering strain B. licheniformis 20085Δcelb was significantly compromised the ability to disintegrate filter paper compared to the original strain. After fermentation for 60 h, the CMCase activity value decreased from 1.86 to 0.50 U/mL, suggesting that the celb gene played an important role in the process of cellulose degradation in B. licheniformis 20085. We also assessed the ability of B. licheniformis 20085Δcelb to pulp bamboo. The yield of bamboo pulp was 51.91%, the kappa number was 11.26%, and 1.3% of cellulose was degraded after bio-pulping. Environmental Scanning Electron Microscope (ESEM) studies were also conducted to visualize the effect of these strains on bamboo cell walls. These results indicate that pulping with B. licheniformis 20085Δcelb can generate a higher yield and lower kappa number.
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