Simultaneous production of single cell protein and killer toxin by Wickerhamomyces anomalus HN1-2 isolated from mangrove ecosystem

Abstract

The yeast Wickerhamomyces anomalus (the previous name was Pichia anomala) HN1-2 isolated from the mangrove ecosystem was found to be able to produce high level of both killer toxin and single cell protein. When the killer yeast cells were grown by batch cultivation in 5-l fermentor, crude protein in the cells, cell mass, reducing sugar, and diameter of the inhibition zone reached 56.0 g per 100 g of cell dry weight, 7.3 g per liter, 9.5 g per liter, and 19.0 mm, respectively within 12 h and this yeast synthesized a large amount of the essential amino acids, such as lysine (7.8%), methionine (1.8%), and leucine (9.0%). The crude killer toxin produced by the killer yeast isolate HN1-2 could kill the cells of Lodderomyces elongisporus, Candida albicans, Metschnikowia bicuspidata, Pichia guilliermondii, Saccharomyces cerevisiae, Yarrowia lipolytica, and Kluyveromyces aestuarii, which were widely distributed in natural marine environments. The results also showed that the undesirable yeast could be avoided during cell growth of the killer yeast.