Production of Starch-Digesting Glucoamylase From Aspergillus Niger ATCC 10864

Production of starch-digesting glucoamylase by Aspergillus niger ATCC 10864 grown in liquid containing 5 types of starch, i.e. soluble starch, corn starch, cassava starch, sticky-rice starch and rice starch was examined. The highest amount of glucoamylase was obtained when rice liquid medium was used as carbon source. The optimal liquid culture conditions for glucoamylase production were as follows: 2% (w/v) rice starch as carbon source mixed with 1% (w/v) peptone (as nitrogen source) and the pH was adjusted to 7.0 followed by shaking in a 30 °C shaking incubator at the speed of 200 rpm. In addition, when the three types of minerals, i.e. CaCl₂·2H₂O, MgSO₄·7H₂O and MnCl₂·4H₂O were added together in the above culture, the yield of glucoamylase was higher than those when each of the three minerals was added separately. Studies on cell growth and glucoamylase in rice liquid medium showed that much more glucoamylase was produced extracellularly during the stationary phase, the experimental phase reaching a maximal activity of about 101.45 U/ml.

Keywords: starch-digesting, glucoamylase, rice liquid medium, Aspergillus niger

Corresponding author: E-mail: cast@kmitl.ac.th