Abstract: The biodegradability of tapioca starch cross linked with phosphorus oxychloride was studied according to the half-vivo model by using micropopulation symbiotic cocultures.The results indicated that the biodegradation rate and degree were slowed down as the degree of cross linking increased.For the samples of a low cross-linked degree,the biodegradation rate sped up and the biodegradation percentage increased as well.When the degree of cross linking was high,starch biodegradation was very difficult.The biodegradability of starch could be regulated by controlling the cross linking degree.

Key words: Tapioca starch , Cross-linked with phosphorus oxychloride, Biodegradability