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Modulation of xylanase production from alkaliphilic Bacillus pumilus VLK-1 through process optimization and temperature shift operation.

ABSTRACT: This study was aimed at enhancing the production of xylanase from an alkaliphilic Bacillus pumilus VLK-1 in submerged fermentation using wheat bran, a cheap and abundantly available agro-residue, through process optimization and to monitor the effect of temperature shift operation on it. The potential of xylanase in saccharification of wheat straw was also investigated. The results showed that optimization of the fermentation process by one variable approach increased the enzyme yield from 402 to 4,986 IU/ml. Subsequently, optimization of nitrogen and carbon sources through response surface methodology led to high level xylanase production (7,295 IU/ml) which was 1.46-fold greater than one variable approach after 56 h of cultivation at 30 °C. Temperature shift operation during fermentation resulted in maximum xylanase production in lesser duration (48 h instead of 56 h). Enzymatic hydrolysis of the alkali pre-treated wheat straw with 500 IU xylanase alone released 173 ± 8 mg sugars/g whereas in combination with cellulase and β-glucosidase released 553 ± 12 mg sugars/g dry substrate in 6 h, indicating its potential in saccharification of the lignocellulosic substrate. Temperature shift operation is likely to be attractive for large scale industrial fermentation due to significant reduction in the operating cost. To our knowledge, this is the first report which showed the effect of temperature shift operation on xylanase production from bacteria. The xylanase production from Bacillus sp. in the present study is close to the highest titre reported in the literature. An enhanced xylanase production using wheat bran, a cheap and abundantly available agro-residue, will apparently reduce the enzyme cost, which would be beneficial for industry.

SUBMITTER: Kumar L

PROVIDER: S-EPMC4145618 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe extracellular xylanase secreted by microorganisms is a hydrolytic enzyme, which arbitrarily cleaves the β-1, 4 backbone of the polysaccharide xylan; an enzyme used in the food processing, bio-pulping and bio-bleaching. The commercial production of the xylanase is limited because of a higher cost involvement, which can be overcome by the cost-effective production of the xylanase through immobilization of the microbial cell by the non-toxic substances.ObjectivesIn this work, the optimization of the extra-cellular cellulase free xylanase production by the immobilized cell of the Bacillus pumilus IMAU80221 strain using Ca-alginate beads along with standardization of the various parameters for a higher xylanase production were studied.Materials and methodsFollowing to sterilization, the Na-alginate solution was mixed with the bacterial suspension of the Bacillus pumilus IMAU80221 and was added drop by drop into the 1 M calcium chloride solution for 1 h for obtaining a uniform sized polymeric bead of the Ca-alginate. For xylanase production, the Ca-alginate beads were then transferred into 100 mL Erlenmeyer flasks with 20 mL of the culture medium containing (w/v) 0.02% NaCl, 0.02% MgSO4, 0.04% (KH4)2PO4, 0.1% peptone, and 0.5% xylan and incubated at 34 °C in an incubator shaker (150 rpm) for 24 h. The resultant supernatant (crude enzyme) was used for enzyme assay.ResultsThe maximum xylanase production by the free cell (1.9 U.mL-1.min-1) was recorded at 48 h which was 40.5% lower than the xylanase production by the immobilized cell (2.67 U.mL-1.min-1) at the same time. The beads containing the immobilized cells could be reused up to eight fermentation cycles for xylanase production and retained 83.5% of the productivity at the fourth cycle. The entrapped cells were stable after six months of storage at 4 °C and retained 68% of the xylanase productivity.ConclusionCellulase free xylanase production from the immobilized Bacillus pumilus IMAU80221 was optimized. The xylanase production by the immobilized cells of Bacillus pumilus was higher by 40.5 and 132.6 % over the free cells respectively after 48 and 72 h of the incubation.

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Modulation of xylanase production from alkaliphilic Bacillus pumilus VLK-1 through process optimization and temperature shift operation.

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