Medium optimization for keratinase production by Bacillus cereus H10 and application of using keratinase in the animal feed
Date Issued
2010
Date
2010
Author(s)
Chung, Chih-I
Abstract
Keratin, which is increasingly accumulating in the environment mainly in the form of feathers and hair, is a part of solid waste management. However, keratin is difficult to degrade due to its highly rigid structure rendered by extensive disulfide bonds and cross-linkages.
In our previous study, we isolated a bacterium with high keratinolytic activity from hog hair and identified as Bacillus cereus H10. The H10 enzyme produced by B. cereus H10 showed high thermal stability and were very effective in hog hair degradation, presenting potential uses for biotechnological processes involving keratin hydrolysis. Thus, in this study, we optimized the culture medium for B. cereus H10 to maximize the H10 enzymes production using a combination of response surface methodology (RSM) and sequential quadratic programming (SQP). Results indicated that B. cereus H10 incubated in a medium with 3.00% hog hair and 1.20% sugar yeast could have the highest cell counts, whereas this strain fermented in the culture medium with 1.06% hog hair and 0.58% glucose could yield the highest keratinolytic activities. After maximization of enzyme production, we further dehydrated the H10 enzyme using spray drying or freeze drying. Both drying methods could remain keratinolytic activity of the H10 enzyme for 6 months at room temperature with no significant difference.
The hog hair meal co-cultured with H10 enzyme showed significantly higher percentages of digestible protein and in vitro digestibility than hog hair meal without the enzyme. However, in vivo study, addition of H10 enzyme did not improve the growth performance of broiler, but H10 enzyme could increased digestibility of high protein content diet of 1 ~ 21-day-old broilers.
In this study, we maximize the production of the H10 enzyme by addition of 1.06% hog hair and 0.58% glucose in the culture medium for B. cereus H10 and dehydration the enzyme using spray drying/freeze drying. The keratinolytic activity of the H10 enzyme was stable for 6 months at room temperature. The in vitro digestibility of poultry indicated that addition of H10 enzyme did not improve the growth performance of broiler, but H10 enzyme could increased digestibility of high protein content diet of 1 ~ 21-day-old broilers.
Subjects
Keratinase
Optimization of medium
Hog hair
SDGs
Type
thesis
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