Effect of initial carbon and nitrogen sources concentrations on growth of Aspergillus awamori and glucoamylase production
A.B. Ariff1* and C. Webb2
1Department of Biotechnology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
2Department of Chemical Engineering, UMIST, P 0 Box 88, Manchester M60 IQD, United Kingdom
(Received 9 February 1998 / Accepted 15 May 1998)
Abstract.
Batch production of glucoamylase by Aspergillus awamori has been studied using different types and concentrations of carbon and nitrogen sources. The fermentations were carried out using an 81 stirred tank fermenter. An initial potato starch concentration of 50 g/l was found optimum for glucoamylase production. When (NH4)2SO4 was used as the sole nitrogen source, irrespective of carbon concentration, an initial concentration of above 7.5 g/l repressed glucoamylase biosynthesis. On the other hand, yeast extract did not show any signs of repression, even though it was used at very high concentration (20 g/l). An initial concentration of yeast extract between 7.5 g/l and 10 g/l was found optimum in terms of yield based on cell mass (Pm/Xm). The addition of small amounts of yeast extract (1-2 g/1) into a medium containing (NH4)2SO4 and starch at a balanced carbon to nitrogen (C/N) ratio increased glucoamylase production greatly. Using 50 g/l potato starch as a carbon source, the maximum glucoamylase concentration obtained using optimized concentration of (NH4)2SO4 yeast extract and a mixture of them were 25.23, 48.77 and 49.62 U/ml, respectively.
Keywords: glucoamylase, Aspergillus awamori, medium optimization, C/N ratiobr
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