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Production and characterization of alkaline protease from hemoglobin-degrading Bacillus pumilus NJM4 to produce fermented blood meal.

ABSTRACT: The aim of the research was to isolate the hemoglobin-degrading bacterial strain to produce fermented blood meal and to characterize the protease produced by this strain. The strain NJM4, a kind of hemoglobin-degrading bacterial strain, was isolated by blood agar plates from slaughterhouse and identified as a Bacillus pumilus by physiological, biochemical, and morphological characteristics and by 16S rRNA gene sequencing. Bacillus pumilus NJM4 could degrade hemoglobin up to 85% in 36 h under the laboratory conditions. The optimal conditions for protease production was achieved at an initial pH level of 8.67, inoculum size of 4%, incubation temperature of 37 °C, and agitation rate 200 rpm. The optimum pH and temperature of hemoglobin-degrading proteases were at 9.0 and 50 °C, respectively. The protease activity was slightly decreased in presence of Ca(2+) and DTT. It was significantly inhibited in the presence of PMSF and EDTA identifying it as alkaline serine-metalloproteinase. Bacillus pumilus NJM4 and hemoglobin-degrading proteases provide potential use for biotechnological process of fermentation and enzymolysis blood meal as animal feed supplement.

SUBMITTER: Yao D

PROVIDER: S-EPMC3550848 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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Production and characterization of alkaline protease from hemoglobin-degrading Bacillus pumilus NJM4 to produce fermented blood meal.

Yao Dawei D Qu Jiao J Chang Peiwei P Tao Yanhua Y Yang Deji D

Journal of food science and technology 20110120 5

The aim of the research was to isolate the hemoglobin-degrading bacterial strain to produce fermented blood meal and to characterize the protease produced by this strain. The strain NJM4, a kind of hemoglobin-degrading bacterial strain, was isolated by blood agar plates from slaughterhouse and identified as a Bacillus pumilus by physiological, biochemical, and morphological characteristics and by 16S rRNA gene sequencing. Bacillus pumilus NJM4 could degrade hemoglobin up to 85% in 36 h under the ...[more]

PMID: 24082276

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Project description:BACKGROUND:Mesophilic alkaline serine proteases from various bacteria have been commercially applied in a range of industries owing to their high catalytic efficiency and wide substrate specificity. However, these proteases have an optimal catalytic temperature of approximately 50 °C, and their activity decreases significantly at low temperature. Therefore, to enhance their cold activity, it is necessary to improve the catalytic performance of these proteases at low temperature. The alkaline serine protease (DHAP) from Bacillus pumilus BA06 is a typical mesophilic enzyme, which has demonstrated great potential in various industrial applications. Here we attempted to improve the cold activity of DHAP via directed evolution. RESULTS:Seven variants (P9S, A1G/K27Q, A38V, A116T, T162I, S182R, and T243S) of DHAP from B. pumilus were obtained via directed evolution. The results showed that all of the variants had increased proteolytic activity at 15 °C towards both the casein and synthetic peptide substrates. With the exception of variant T243S, the thermostability of these variants did not decrease in comparison with the wild-type enzyme. Kinetic analysis indicated that the increase in catalytic efficiency was largely attributed to the increase in turnover number (kcat). Furthermore, the combined variants generated by site-directed mutagenesis showed a further increase in specific caseinolytic activity and the kcat value for hydrolysis of the synthetic peptide. The combined variants of P9S/K27Q and P9S/T162I exhibited an approximate 5-fold increase in caseinolytic activity at 15 °C and almost no loss of thermostability. Finally, the possible mechanism responsible for the change in catalytic properties for these variants was interpreted based on structural modeling. CONCLUSIONS:Directed evolution and site-directed mutagenesis were combined to engineer variants of the DHAP from B. pumilus. All of the variants exhibited an increase in hydrolytic efficiency at low temperature towards both of the substrates, casein and synthetic peptide, without any loss of thermostability compared with the wild-type. These data suggest that engineering low-temperature activity for a bacterial protease is not always associated with the loss of thermostability. Furthermore, our findings demonstrate that enhanced cold activity and thermostability could be integrated into a single variant.

Project description:BACKGROUND:Bacillus licheniformis 2709 is extensively applied as a host for the high-level production of heterologous proteins, but Bacillus cells often possess unfavorable wild-type properties, such as production of viscous materials and foam during fermentation, which seriously influenced the application in industrial fermentation. How to develop it from a soil bacterium to a super-secreting cell factory harboring less undomesticated properties always plays vital role in industrial production. Besides, the optimal expression pattern of the inducible enzymes like alkaline protease has not been optimized by comparing the transcriptional efficiency of different plasmids and genomic integration sites in B. licheniformis. RESULT:Bacillus licheniformis 2709 was genetically modified by disrupting the native lchAC genes related to foaming and the eps cluster encoding the extracellular mucopolysaccharide via a markerless genome-editing method. We further optimized the expression of the alkaline protease gene (aprE) by screening the most efficient expression system among different modular plasmids and genomic loci. The results indicated that genomic expression of aprE was superior to plasmid expression and finally the transcriptional level of aprE greatly increased 1.67-fold through host optimization and chromosomal integration in the vicinity of the origin of replication, while the enzyme activity significantly improved 62.19% compared with the wild-type alkaline protease-producing strain B. licheniformis. CONCLUSION:We successfully engineered an AprE high-yielding strain free of undesirable properties and its fermentation traits could be applied to bulk-production by host genetic modification and expression optimization. In summary, host optimization is an enabling technology for improving enzyme production by eliminating the harmful traits of the host and optimizing expression patterns. We believe that these strategies can be applied to improve heterologous protein expression in other Bacillus species.

Dataset Information

Production and characterization of alkaline protease from hemoglobin-degrading Bacillus pumilus NJM4 to produce fermented blood meal.

Publications

Production and characterization of alkaline protease from hemoglobin-degrading Bacillus pumilus NJM4 to produce fermented blood meal.

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