Journal of Pure and Applied MicrobiologyVol. 7 No. 4

Enhancement of Amphibacillus sp NPST-10 Cyclodextrin Glucanotransferase Production by Optimizing Physio-Environmental Factors

Abdelnasser S. S. Ibrahim1,2*, Ali A. Al-Salamah1, Mohamed A. El-Tayeb1 and Yahya B. El-Badawi1

1Department of Botany and Microbiology, College of Science, King Saud University, Riyadh - 11451, Saudi Arab. 2National Research Center, El-Buhouth St., Dokki, Cairo 12311, Egypt.

Received on 20 January 2013 and accepted on 02 March 2013

 

ABSTRACT

The present study was conducted to optimized culture conditions and environmental factors that enhance cyclodextrin glucanotransferase (CGTase) production by a previously isolated, new alkaliphilic Amphibacillus sp. NPST-10. Production of CGTase was growth-associated, with enzyme synthesis starting during the early exponential-growth phase and increasing as the cells grew exponentially, reaching the highest concentration levels (0.6 U/ml) at the end of the stationary growth phase (38 h) and remaining constant during prolonged incubation up to 60 h. While mono- and disaccharides supported Amphibacillus sp. NPST-10 growth, maximal CGTase production was detected using various types of starch as the main carbon source, with maximum enzyme production observed with 1.75% soluble starch. Organic nitrogen sources enhanced CGTase production, with a mixture of peptone, yeast extract, and casamino acids (1.2% w/v) supporting maximal production. In addition, Amphibacillus sp. NPST-10 was able to grow in a wide range of NaCl concentrations up to 15%, with maximal growth and CGTase production at 6% and 3%, respectively, indicating the halophilic nature of this bacterium. Furthermore, maximal Amphibacillus sp. NPST-10 growth and CGTase production were detected at pH 9.5 and 9.0, respectively, indicating that Amphibacillus sp. NPST-10 is alkaliphilic in nature. Moreover, maximum enzyme production was observed at 35?C with aeration by shaking at 150 rpm. Addition of Zn2+, Cu2+, Co2+, or Ba2+ ions led to reductions both in bacterial growth and CGTase production, particularly at a high metal concentration (10 mM), by approximately 83.6%, 72.7%, 57.6%, and 31.6%, respectively. However, inclusion of Ca2+ ions in the culture medium led to a significant increase in CGTase production of approximately 16%. These results indicated that optimizing the culture medium and environmental conditions increased Amphibacillus sp. NPST-10 CGTase production by approximately two fold.

Keywords : Cyclodextringlucanotransferase, Amphibacillus sp, Alkaliphiles, Optimization, Production.