Date Published: May 25, 2011
Author(s): Miyoshi Kato, Haruyuki Iefuji.
We previously developed a host vector system for the wastewater treatment yeast Hansenula fabianii J640. The promoter and terminator regions of the gene encoding glucoamylase from H. fabianii J640 were used for a new expression vector, pHFGE-1. The performance of pHFGE-1 was compared with that of the widely used pG-1 transformant vector. H. fabianii J640 (HF-TAMY) cells were transformed with pHFGE-1, and Saccharomyces cerevisiae YPH-499 (SC-TAMY) cells were transformed with pG-1, both of which carried the Taka-amylase. Expression of Taka-amylase by HF-TAMY showed higher than that by SC-TAMY. By using this new system, we bred the new wastewater treatment yeast that shows α-amylase activity. This yeast appears to grow well under experimental wastewater conditions, and is effective in treating model wastewater containing soluble and insoluble starch.
Many food factories use wastewater treatment systems that use yeasts (Yoshizawa 1978, 1981, Sato et al. 1986, Moriya et al. 1990, Suzuki et al. 1991, Suzuki et al. 1996). However, some wastewater-containing polysaccharides, such as raw starch and hemicellulose, are difficult to treat because presently used yeasts secrete few enzymes that can digest these polysaccharides. One way to treat these wastewaters is to transform conventional wastewater treatment yeasts with the genes for polysaccharide-digesting enzymes such as raw starch-digesting α-amylase and acid xylanase.
We developed a host vector system for the wastewater treatment yeast, H. fabianii J 640, and we created new wastewater treatment yeast transformants (HF-XYN and HF-AAMY). The expression of the foreign gene that was integrated in the transformant was induced by maltose and repressed by glucose. However, the growth rates of the transformants carrying pHFGE-1 and the widely used pG-1 were the same and both transformants strongly expressed the foreign gene, even in medium containing glucose, which was expected to repress expression of the foreign gene. Our host vector system strongly expresses the foreign gene. Because wastewater contains various components, the strong expression of the new strain is an advantage. The HF-AAMY cells were effective in treating the model wastewater.
The authors declare that they have no competing interests.