The bacteria involved in the biodegradation of Enteromorpha prolifera (EP) are largely unknown, especially in offshore mangrove environments. In order to obtain the bacterial EP-degrading communities, sediments from a typical mangrove forest were sampled on the roots of mangrove in Dongzhai Port (Haikou, China). The sediments were enriched with crude EP powders as the sole carbon source. The bacterial composition of the resulting mangrove-degrading micro-community (MDMC), named D2-1, was analysed. With methods of plate cultivation and polymerase chain reaction-denaturing gradient gel electrophoresis and 16S rRNA library analysis, 18 bacteria belonging to nine genera were detected from this community. Among these detected bacteria, five major bands closely related to Bacillus, Marinobacter, Paenibacillus, Photobacterium, and Zhouia were determined. A novel two-step pretreatment for EP was proposed to lower the severity requirement of biodegraded pretreatment time. It consisted of a mild physical or chemical step (ultrasonic or H(2)O(2)) and a subsequent biological treatment with community D2-1. The combined treatment led to significant increases in the EP degradation. After combined treatment, the net yields of total soluble sugars and reducing sugars increased. The combined pretreatment of H(2)O(2) (2%, 48 h) and MDMC (7 days) was more effective than the treatment of MDMC only for 15 days. It could remarkably shorten the residence time and reduce the losses of carbohydrates.