Molecular characterization and metabolic profiling of banana (Musa × paradisiaca L.) pseudostem waste degrading microbes”
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Date
2015
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Publisher
NAU
Abstract
Six different bacterial isolates were isolated from the different decomposing samples of the banana collected. These were distinct and named as Bacillus licheniformis NAULH-1, Bacillus wakoensis NAULH-
2, Bacillus licheniformis NAULH-3, Bacillus wakoensis NAULH-4, Serratia marcescens NAULH-5 & Brevibacillus agri NAULH-6, respectively. Cellulase (cell), β-glucosidase (Bgl) and exoglucanase
(Exgl) gene were present in all six isolates. Laccase (Cot A) and xylanase (xyn) gene was present only in four isolates viz., Bacillus licheniformis NAULH-1, Bacillus wakoensis NAULH-2, Bacillus licheniformis
NAULH-3, Bacillus wakoensis NAULH-4. Lignin perooxidase (Lip) gene was found in three isolates (Bacillus licheniformis NAULH-1, Bacillus wakoensis NAULH-2, Bacillus wakoensis NAULH-4) only. Partial sequencing of the laccase gene of all four isolates indicated the presence of Cot-A conserved domain of cupredoxin superfamilies. B. wakoensis NAULH-2 showed CuRo_1_BOD_Cot-A like domain at 1- 140 amino acid sequence having trinuclear copper binding site at 70-122 amino acid sequence. B. licheniformis NAULH-1 had 169 amino acid sequences having two conserve domains of CuRo_2 _Cot-A and CuRo_3
_Cot-A having 1-27 and 55-166 amino acid sequence, respectively. B. licheniformis NAULH-3 had only one domain CuRo_1_BOD_Cot-A domain having 37-111 amino acid sequence, while B. wakoensis
NAULH-4 contained two conserve domains CuRo_1_BOD_Cot-A and CuRo_2 _Cot-A having 1-22 and 33-51 amino acid sequence respectively. The data revealed by 16s rDNA sequencing indicated that B. wakoensis NAULH-2 and B. wakoensis NAULH-4 had 99% similarity with the Bacillus sp., while B. licheniformis NAULH-1 and B. licheniformis NAULH-3 showed 99% similarity with Bacillus licheniformis. All six isolates showed production of endoglucanse, exoglucanase and β-glucosidase enzymes. Four isolates viz., B. licheniformis NAULH-1, B. wakoensis NAULH-2, B. licheniformis NAULH-1 and B. wakoensis NAULH-4 produced laccase and xylanase enzymes. The phenotypic microarray of metabolic profiling indicated that all bacterial isolates have specific ability to utilize complex carbohydrates except Brevibacillus agri NAULH-6. In banana pseudostem degradation facilities B. wakoensis NAULH-2 showed fastest and highest degradation
of banana pseudostem at neutral pH, while B. wakoensis NAULH-4 showed higher degradation at alkaline pH 8. B. licheniformis NAULH-1 degraded higher amount of banana pseudostem at 30-35OC compare to all
isolates, while at higher temperature 40-45OC, B. wakoensis NAULH-2, B. licheniformis NAULH-3 and B. wakoensis NAULH-4 degraded higher amount of banana pseudostem. All the isolates showed optimum efficacy of banana pseudostem degradation at 28 days. Laccase produced by Cot A gene is the major enzyme responsible for lignin degradation. Till date fungal laccase were used for lignin degradation, which is the major obstacle in degradation of banana pseudostem. The identification of new bacterial laccases gene would open up new perspectives for rapid biotransformation of the cumbersome waste in to carbon rich substances for the eco-friendly agriculture
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Keywords
enzymes, productivity, bacteria, acidity, aromatic compounds, polysaccharides, bananas, cellulose, genes, fungi