Enhanced Activity of Intracellular Agarase from a Novel Marine Strain Agarivorans gilvus WH0801

A marine bacterium strain Agarivorans gilvus WH0801 with the efficient agar degradation ability isolated from fresh seaweed samples of Weihai coast was found to be potential in producing agarase. We studied on the optimal medium composition and culture conditions of Agarivorans gilvus WH0801 by statistical methods in shake flasks. First, several more important factors influencing agarase activity were selected by Plackett-Burman design. They are agar concentration, yeast extract concentration and seed age. Then the optimum levels of these three variables were further determined using Box-Behnken design. The highest agarase activity is obtained in the medium consisting of 2.49 g L-1 agar and 0.88 g L-1 yeast extract when the seed age is 25.64 h. The levels of other factors are 1 g L-1 peptone, 0.01 g L-1 ironic citrate at initial pH 7.0 and 28 °C. The whole optimization strategy results in the activity of agarase reaches 1.158 U mL-1, which is about 6.2-fold increase compares with the control.

Sequence Analysis of a 101-Kilobase Plasmid Required for Agar Degradation by a MicroscillaIsolate

ABSTRACT An agar-degrading marine bacterium identified as aMicroscilla species was isolated from coastal California marine sediment. This organism harbored a single 101-kb circular DNA plasmid designated pSD15. The complete nucleotide sequence of pSD15 was obtained, and sequence analysis indicated a number of genes putatively encoding a variety of enzymes involved in polysaccharide utilization. The most striking feature was the occurrence of five putative agarase genes. Loss of the plasmid, which occurred at a surprisingly high frequency, was associated with loss of agarase activity, supporting the sequence analysis results.