African Journal of Biotechnology Vol. 4 (10), pp. 1089-1094, October 2005          
ISSN 1684–5315 © 2005 Academic Journals

Full Length Research Paper

Nutritional composition of sorghum bicolor starch hydrolyzed with amylase from Rhizopus sp.

ADEBIYI A. O¹*, ADEBIYI, A. P², AND OLANIYI, E.O.¹

¹Pure and Applied Biology Department, Ladoke Akintola University of Technology, P.M.B 4000, Ogbomoso, Nigeria.

²Food Science and Engineering Department, Ladoke Akintola University of Technology, Ogbomoso, Nigeria.

*Corresponding author. E-mail: ayobayomitale@yahoo.com.

Accepted 31 August, 2005

The partially purified amylase extracted from a local isolate of Rhizopus sp. was used for hydrolysis of Sorghum bicolor starch. The amylolytic activity of the enzyme was 45.33 U/g and the protein content was 0.345 mg/ml. The maximum temperature for the enzyme was obtained at 55°C while it acts best at pH 5.0. The percentage increase of 1.62, 21.00 and 1.42% for the fat, protein and carbohydrate respectively for the hydrolysed sorghum starch compared with the unhydrolysed sorghum starch was recorded. The increase in the vitamin B1 and B2 of the hydrolysed sorghum starch over the unhydrolysed starch was 2.93 and 2.39%, respectively. A percentage increase of 9.10, 0.89 and 2.83% for Ca, Mg and Na, respectively, for the hydrolysed sorghum starch over the unhydrolysed starch sample was recorded. The Thin Layer Chromatogram of the hydrolysed sorghum starch revealed the presence of the following essential amino acids; histidine, methionine, threonine, isoleucine, phenylalanine, tryptophan and valine. The chromatographic and quantitative analysis of the hydrolysed sorghum starch shows that it contains three oligosaccharides; sucrose (7.38%), lactose (1.75%) and maltose (48.0%), and two monosaccharides which are glucose (1.75%) and galactose (1.16% ).

Key words:  Sorghum, amylase, pH, temperature, hydrolysis, essential amino acids.