Inducing Cellulase Activity of Microbulbifer Hydrolyticus Using Hot-Water Wood Extract As Substrate
This study used wood extract from Paulownia elongata (WE) and hydrolisate of sugar maple (hydrolysate) produced during hot-water extraction as substrates to stimulate the production of cellulase from Microbulbifer hydrolyticus IRE-31(ATCC 700072). Selective strain medium adaptation of the original wild M. hydrolyticus IRE31 was performed in order to improve bacterial growth in mediums supplemented with hydrolysate and WE. Comparative studies were performed to establish better bacterial growth conditions and enzymatic activity at a given temperature , agitation and medium pH. The effect of different substrates , growth supplements and bases utilized to control the medium pH were among the studies evaluated. Flask tests where pure marine broth medium with an enzymatic activity of 0.009 U/ml broth medium was used as control and compared it to mediums supplemented with xylose , glucose , cellobiose , hydrolisate , WE or yeast extract , showed higher cellulase activity in the sample broth containing either WE or hydrolisate. No discernible activity was revealed in broths containing either glucose or xylose. Scale up from shake flask incubations to 1L stirred tank bioreactor set at pH 7.5, 37˚C and 300 rpm, and supplemented with 15% (v/v) HWEP or 10% (v/v) HWH, yielded a maximum crude enzymatic activity of 3.004U/ml and 0.840 U/ml; respectively.. These results reveal a significant increase in cellulase activity with growth mediums supplemented with complex substrates containing xylooligosaccharides such as P. elongata wood extract and sugar maple hydrolysate.
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