Fish skin bacteria: Production of friction-reducing polymers

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Abstract
The supernatant fluids of cultures of four bacterial strains isolated from the skin of barracuda contained extracellular polymer concentrations of 0.2–0.5 mg/ml and reduced factional drag by 2.5–22% in a turbulent flow rheometer. The production and properties of one of the drag-reducing polymers, referred to as PS-6, were studied further. Polymer PS-6 was produced by strain NS-31 in minimal salts medium supplemented with ethanol or glucose. The polymer began to accumulate in the culture medium during exponential phase and continued to be produced during stationary phase. It reduced drag by 55% at a concentration of 0.75 mg/ ml. Acid-base titration of the deproteinized polymer PS-6A gave two inflection points: pK1=3.26 (2.4 μeq/mg) and pK2=9.66 (0.8 μeq/mg).13C-NMR spectroscopy of PS-6A resolved 25 peaks, including three methyl groups, three carbonyl groups, and four signals in the anomeric region (99–103 ppm), indicating the presence of four different monosaccharides. Strong acid hydrolysis of PS-6A yielded an amino acid, pyruvate, and four reducing sugars: a hexosamine, a uronic acid, and two hexoses which migrated on TLC similarly to glucose and galactose. The possible role of bacteria in production of drag-reducing mucus is discussed.