Antiadhesive activity of poly-hydroxy butyrate biopolymer from a marine Brevibacterium casei MSI04 against shrimp pathogenic vibrios.

BACKGROUND: Vibrio pathogens are causative agents of mid-culture outbreaks, and early mortality syndrome and secondary aetiology of most dreadful viral outbreaks in shrimp aquaculture. Among the pathogenic vibrios group, Vibrio alginolyticus and V. harveyi are considered as the most significant ones in the grow-out ponds of giant black tiger shrimp Penaeus monodon in India. Use of antibiotics was banned in many countries due to the emergence of antibiotic-resistant strains and accumulation of residual antibiotics in harvested shrimp. There is an urgent need to consider the use of alternative antibiotics for the control of vibriosis in shrimp aquaculture. Biofilm formation is a pathogenic and/or establishment mechanism of Vibrio spp. This study aims to develop novel safe antibiofilm and/or antiadhesive process using PHB to contain vibrios outbreaks in shrimp aquaculture. RESULTS: In this study a poly-hydroxy butyrate (PHB) polymer producing bacterium Brevibacterium casei MSI04 was isolated from a marine sponge Dendrilla nigra and production of PHB was optimized under submerged-fermentation (SmF) conditions. The effect of carbon, nitrogen and mineral sources on PHB production and enhanced production of PHB by response surface methods were demonstrated. The maximum PHB accumulation obtained was 6.74 g/L in the optimized media containing 25 g/L starch as carbon source, 96 h of incubation, 35°C and 3% NaCl. The highest antiadhesive activity upto 96% was recorded against V. vulnificus, and V. fischeri, followed by 92% against V. parahaemolyticus and V. alginolyticus and 88% inhibition was recorded against V. harveyi. CONCLUSION: In this study, a thermostable biopolymer was chemically characterized as PHB based on 1HNMR spectra, FT-IR and GC-MS spectra. The NMR spectra revealed that the polymer was an isocratic homopolymer and it also confirmed that the compound was PHB. The antiadhesive activity of PHB was determined in microtitre plate assay and an effective concentration (EC) of PHB (200 µl containing 0.6 mg PHB) was confirmed by confocal laser scanning microscopic analysis of vibrio biofilm on pre-treated glass and polystyrene surfaces. This is a first report on anti-adhesive activity of PHB against prominent vibrio pathogens in shrimp aquaculture.

Effect of Fe nanoparticle on growth and glycolipid biosurfactant production under solid state culture by marine Nocardiopsis sp. MSA13A.

BACKGROUND: Iron is an essential element in several pathways of microbial metabolism, and therefore low iron toxicity is expected on the usage of Fe nanoparticles (NPs). This study aims to determine the effect of Fe NPs on biosurfactant production by marine actinobacterium Nocardiopsis sp. MSA13A under solid state culture. Foam method was used in the production of Fe NPs which were long and fiber shaped in nature. RESULTS: The SEM observation showed non toxic nature of Fe NPs as no change in the morphology of the filamentous structure of Nocardiopsis MSA13A. The production of biosurfactant by Nocardiopsis MSA13A under solid state culture supplemented with Fe NPs increased to 80% over control. The biosurfactant produced by Nocardiopsis MSA13A was characterized as glycolipid derivative which effectively disrupted the pre-formed biofilm of Vibrio pathogen. CONCLUSION: The use of metal NPs as supplement would reduce the impact of non-metallic ions of the metal salts in a fermentation process. This would ultimately useful to achieve greener production process for biosurfactants. The present results are first report on the optimization of biosurfactant production under SSC using Fe NPs.