Bikash Chandra Behera

Impact of heavy metals on bacterial communities from mangrove soils of the Mahanadi Delta (India)

This study aimed to assess soil nutrient status and heavy metal content and their impact on the predominant soil bacterial communities of mangroves of the Mahanadi Delta. Mangrove soil of the Mahanadi Delta is slightly acidic and the levels of soil nutrients such as carbon, nitrogen, phosphorous and potash vary with season and site. The seasonal average concentrations (μg/g) of various heavy metals were in the range: 14 810–63 370 (Fe), 2.8–32.6 (Cu), 13.4–55.7 (Ni), 1.8–7.9 (Cd), 16.6–54.7 (Pb), 24.4–132.5 (Zn) and 13.3–48.2 (Co). Among the different heavy metals analysed, Co, Cu and Cd were above their permissible limits, as prescribed by Indian Standards (Co=17 μg/g, Cu=30 μ g/g, Cd=3–6 μ g/g), indicating pollution in the mangrove soil. A viable plate count revealed the presence of different groups of bacteria in the mangrove soil, i.e. heterotrophs, free-living N2 fixers, nitrifyers, denitrifyers, phosphate solubilisers, cellulose degraders and sulfur oxidisers. Principal component analysis performed using multivariate statistical methods showed a positive relationship between soil nutrients and microbial load. Whereas metal content such as Cu, Co and Ni showed a negative impact on some of the studied soil bacteria.

Phosphate solubilization and acid phosphatase activity of Serratia sp. isolated from mangrove soil of Mahanadi river delta, Odisha, India

Phosphorus is an essential element for all life forms. Phosphate solubilizing bacteria are capable of converting phosphate into a bioavailable form through solubilization and mineralization processes. Hence in the present study a phosphate solubilizing bacterium, PSB-37, was isolated from mangrove soil of the Mahanadi river delta using NBRIP-agar and NBRIP-BPB broth containing tricalcium phosphate as the phosphate source. Based on phenotypic and molecular characterization, the strain was identified as Serratia sp. The maximum phosphate solubilizing activity of the strain was determined to be 44.84 μg/ml, accompanied by a decrease in pH of the growth medium from 7.0 to 3.15. During phosphate solubilization, various organic acids, such as malic acid (237 mg/l), lactic acid (599.5 mg/l) and acetic acid (5.0 mg/l) were also detected in the broth culture through HPLC analysis. Acid phosphatase activity was determined by performing p-nitrophenyl phosphate assay (pNPP) of the bacterial broth culture. Optimum acid phosphatase activity was observed at 48 h of incubation (76.808 U/ml), temperature of 45 °C (77.87 U/ml), an agitation rate of 100 rpm (80.40 U/ml), pH 5.0 (80.66 U/ml) and with glucose as a original carbon source (80.6 U/ml) and ammonium sulphate as a original nitrogen source (80.92 U/ml). Characterization of the partially purified acid phosphatase showed maximum activity at pH 5.0 (85.6 U/ml), temperature of 45 °C (97.87 U/ml) and substrate concentration of 2.5 mg/ml (92.7 U/ml). Hence the present phosphate solubilizing and acid phosphatase production activity of the bacterium may have probable use for future industrial, agricultural and biotechnological application.

Microbial cellulases – Diversity & biotechnology with reference to mangrove environment: A review

Cellulose is an abundant natural biopolymer on earth, found as a major constituent of plant cell wall in lignocellulosic form. Unlike other compounds cellulose is not easily soluble in water hence enzymatic conversion of cellulose has become a key technology for biodegradation of lignocellulosic materials. Microorganisms such as aerobic bacteria, fungi, yeast and actinomycetes produce cellulase that degrade cellulose by hydrolysing the β-1, 4-glycosidic linkages of cellulose. In contrast to aerobic bacteria, anaerobic bacteria lack the ability to effectively penetrate into the cellulosic material which leads to the development of complexed cellulase systems called cellulosome. Among the different environments, the sediments of mangrove forests are suitable for exploring cellulose degrading microorganisms because of continuous input of cellulosic carbon in the form of litter which then acts as a substrate for decomposition by microbe. Understanding the importance of cellulase, the present article overviews the diversity of cellulolytic microbes from different mangrove environments around the world. The molecular mechanism related to cellulase gene regulation, expression and various biotechnological application of cellulase is also discussed.

Cellulase from Bacillus licheniformis and Brucella sp. isolated from mangrove soils of Mahanadi river delta, Odisha, India

Abstract In the present study, two cellulose-degrading bacteria (CDB-5 and CDB-12) were isolated from mangrove soils of Mahanadi river delta, based on halo zone formation in Congo red agar medium and evaluation for cellulase production in CMC broth medium. Based on morphological, biochemical and 16S rRNA gene sequencing, the two strains, CDB-5 and CDB-12, were identified as Brucella sp. and Bacillus licheniformis, respectively. The gene bank accession number of the strains CDB-5 and CDB-12 are KR632646 and KR632645, respectively. The strain Brucella sp. and B. licheniformis showed an enzyme activity of 96.37 U/ml and 98.25 U/ml, respectively, after 72 h of incubation period. Enzyme production was optimized under different growth conditions such as pH, temperature, agitation rate, carbon source, sodium chloride (NaCl), and nitrogen sources. Maximum cellulase production by both the strains was obtained in the same parameter condition such as pH (7.0), rpm (150), and NaCl (2%, w/v) which varies for other parameters. The strain, CDB-5, produced maximum cellulase at 35 °C temperature, maltose as a carbon source, and yeast extract as a nitrogen source where as the strain CDB-12 produces maximum cellulase at 45 °C temperature, carboxyl methyl cellulose (CMC) as carbon source and trypton as a nitrogen source. The bacterial crude enzyme was purified by ammonium sulfate precipitation followed by overnight dialysis. SDS-PAGE analysis of the partially purified cellulase enzyme exhibited band sizes of approximately 55 and 72 kDa.

Ethanol production by a cellulolytic fungus Aspergillus terreus NCFT 4269.10 using agro-waste as a substrate

ABSTRACT Aspergillus terreus NCFT 4269.10 was evaluated for the production of cellulase by liquid state surface fermentation (LSSF), liquid shaking fermentation (LShF) and solid state fermentation (SSF). Maximum cellulase production was observed in LSSF (344.88 ± 3.5U/ml) when banana peel (BP) was used as the substrate followed by wheat bran (WB) and sawdust (SD). The total protein content was 1160.72 ± 2.7 µg/ml when SSF was carried. It was observed that maximum biomass of A. terreus was obtained with WB (0.55 ± 0.07 g/50 ml) as compared to other substrates. Immobilized spores of A. terreus applied for fermentation study revealed maximum cellulase activity (809.38 ± 2.7 U/ml) with BP up to the second cycle and decreased thereafter. The secretion of protein content was noticed at every cycle and continued up to the fifth cycle displaying a peak at the fourth cycle (2243.83 ± 9.7 µg/ml ml) when SD was used as the substrate. It is observed that the third flask containing S. cerevisiae substrate with cellulase was able to produce the highest amount of alcohol (19.8 g/L) with high purity (1.9%) as compared to the substrate with S. cerevisiae (7.9 g/L) and co-cultivated fermentation conditions (4 g/L).