Search

Aims: To investigate early marine biofilm-forming bacterial diversity on immersed antimicrobial-free commercial paint substratum in seawater. Methodology and results: Total ten bacterial strains were successfully isolated and identified by complete 16S rRNA sequencing. The isolates morphological, biochemical properties, biofilm-forming ability, extracellular polymeric substance (EPS) productivity and components were characterised. The morphological and biochemical characterization of the strains showed strains-specific variation. All isolates were strong biofilm producers with four motile strains being both flat-bottom and air-liquid-interface biofilm producers, while other strains were only air-liquid interface biofilm producer. Based on 16S rRNA, three strains were identified as Marinomonas communis, two were Marinomonas sp., while the rest were Alteromonas litorea, Alteromonas sp., Salinimonas lutimaris, Idiomarine baltica and Bacillus niabensis. The amount of EPS that the isolates produced ranged from 1.95 to 2.89 g/L and productivity of EPS was inversely correlated with the cell biomass. Analysis of the extracted EPS using attenuated total reflectance-fourier transform infrared (ATR-FTiR) showed that all isolates EPS contained carbohydrates, nucleic acid, protein, DNA/RNA and lipid. Conclusion, significance and impact of study: Bacterial diversity in early stages of biofilm on the commercial paint surface was dominated by Gram-negative bacteria from Gammaproteobacteria class. Isolates with superior cell growth showed lowest EPS production. This finding was expected to provide knowledge on distribution of different marine bacterial species in the biofilm on paint coated surfaces which may beneficial to formularize a new antibiofilm paint additive. [ABSTRACT FROM AUTHOR]

The cations are needed as stimulants for effective flocculation by the cation-dependent bioflocculants. Addition of metal ions (cations) can counterbalance anionic functional groups of both bioflocculant and solid particles thereby increasing the bioflocculant adsorption to suspended particles. In the present study, addition of all dose of both Ca2+ and Mg2+ stimulated the efficiency of the bioflocculant with optimum flocculation efficiency of 95% recorded with 5 mL of 1% Ca2+. While lower dose (1 - 2 mL) of Al3+ also stimulated the bioflocculant to about 94%, Na+ and Fe3+ inhibited flocculation at all doses tested. K+ slightly enhanced the flocculation at 4 - 10mL of 1%. The present cationic bioflocculant can be suggested as a substitute for chemical flocculants. [ABSTRACT FROM AUTHOR]