ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Rhizopus stolonifer LAU 07: a novel source of fructosyltransferase

Agbaje Lateef, Julius K. Oloke, Evariste B. Gueguim Kana, Solomon O. Oyeniyi, Olukemi R. Onifade, Ayokunmi O. Oyeleye, and Olabiyi C. Oladosu

Biotechnology Group, Microbiology Unit, Department of Pure and Applied Biology, Ladoke Akintola University of Technology, PMB 4000 Ogbomoso, Nigeria

E-mail: agbaje72@yahoo.com

Received: 6 February 2008  Revised: 23 March 2008  Accepted: 24 March 2008

Abstract: Increasing awareness of the importance of fructooligosaccharides (FOS) as ingredients of functional foods has led to intensive search of new sources of fructosyltransferases (FTase), enzymes responsible for the conversion of sucrose to fructooligosaccharides. A local strain of Rhizopus stolonifer isolated from spoilt orange fruit with high fructosyltransferase activity (U _t) of 12.31–45.70 U mL⁻¹ during a fermentation period of 24–120 h is herein reported. It showed low hydrolytic activity (U _h) in the range of 0.86–1.78 U mL⁻¹ during the same period. FOS yield of 34 % (1-kestose, GF₂, nystose, GF₃) was produced by FTase obtained from a 72 h-old culture using 60 g of sucrose per 100 mL of the substrate. When the isolate was grown in a defined submerged medium, its pH dropped sharply from the intial value of 5.5 to 1.0 within 24 h, and this value was maintained throughout the fermentation. The biomass content ranged from 8.8 g L⁻¹ at 24 h of fermentation to reach the maximum of 10 g L⁻¹ at 72 h. It was reduced to 5.6 g L⁻¹ at the end of 120 h of fermentation. This report represents the first reference to a strain of Rhizopus as a source of FTase for the production of FOS. The high U _t/U _h ratio shown by this isolate indicates that it may be a good strain for the industrial and commercial production of FOS. However, there is a need of further optimization of the bioprocess to increase the conversion efficiency of sucrose to FOS by the enzyme.

Keywords: Rhizopus  - submerged fermentation - fructosyltransferase - fructooligosaccharides

Full paper is available at www.springerlink.com.

DOI: 10.2478/s11696-008-0074-3

Chemical Papers 62 (6) 635–638 (2008)