Yoshitake Higuchi

Alpha-Amylase Activity of Starch Degrading Bacteria in Digested Sludge

Akiyoshi Ohashi, Hiroyuki Imachi and Hideki Harada

Anaerobic treatment of solid waste is commonly operated at lower organic loading rates compared to those of wastewater, mainly due to relatively slow hydrolysis of organic solids, which is usually considered to be a rate-limiting step. It is essential to enhance the capability of anaerobic process through elucidation of more precise mechanism on hydrolysis, especially for solid waste treatment.
It is still unclear how microorganisms attack and hydrolyze solid wastes in digested sludge, i.e., whether the hydrolytic enzyme is active in soluble form in bulk liquid or on the surface of microbial cell wall. There is still little knowledge on fundamental information on the microorganisms that are responsible for hydrolysis of organic solids and the influence of substrate type on hydrolysis activity per cell.
Present study attempts to answer these questions. We focused on alpha-amylase, which is one of hydrolytic enzymes. Hydrolysis of solid starch was investigated with several anaerobic batch experiments. Activity of alpha-amylase was estimated and solid starch-degrading bacteria were successfully isolated. Monitoring of the isolated bacteria was done by fluorescence in situ hybridization (FISH).