Enhanced β-mannanase production by Bacillus licheniformis by optimizing carbon source and feeding regimes

Bacillus licheniformis HDYM-04 was isolated in flax retting water and showed β-mannanase activity. Carbon sources for β-mannanase production, as well as the fermentation conditions and feeding strategy, were optimized in shake flasks. When glucose or konjac powder was used as the carbon source, the β-mannanase activity was 288.13 ± 21.59 U/mL and 696.35 ± 23.47 U/mL at 24 h, respectively, which was approximately 4.4- to 10.68-fold higher than the values obtained with wheat powder. When 0.5% (w/v) glucose and 1% (w/v) konjac powder were added together, maximum enzyme activities of 789.07 ± 25.82 U/mL were obtained, an increase of 13.35% compared to the unoptimized cultures with only 1% (w/v) konjac powder. The enzyme activity decreased in the presence of 1% (w/v) konjac powder, but the highest enzyme activity was 1,533.26 ± 33.74 U/mL, a 1.2-fold increase compared with that in nonoptimized cultures; when 0.5% (w/v) glucose was used, the highest enzyme activity was 966.53 ± 27.84 U/mL, an increase in β-mannanase activity of 38.79% compared with control cultures. In this study, by optimizing fed-batch fermentation conditions, the yield of β-mannanase produced by HDYM-04 was increased, laying the foundation for the industrial application and further research of B. licheniformis HDYM-04.