EVALUATION OF CANDIDA-BLANKII HYBRIDS FOR BIOMASS PRODUCTION

The cell size of a diploid Candida blankii isolate (UOVS-64.2), a yeas t with potential for use in single cell protein production from hemice llulose hydrolysates, was increased by intraspecific protoplast fusion of auxotrophic mutants produced by UV irradiation followed by nystati n enrichment. Protoplast fusion yielded an isolate (UOVS-P2) which had a mean cell volume of approximately three times that of the parental strain. This isolate was not a true tetraploid but rather an aneuploid strain. Its maximum specific growth rate was only 40% that of the par ental strain and the cell and protein yields were also appreciably low er. During continuous cultivation in simulated bagasse hemicellulose h ydrolysate, isolate UOVS-P2 proved unstable and a spontaneous reductio n in ploidy occurred. A new isolate (UOVS-PB2) originating from this c ulture had a 43% higher mean cell volume and contained approximately 1 3% more DNA than the parental strain (UOVS-64.2). In simulated hemicel lulose hydrolysate the cell and protein yields of isolate UOVS-PB2 wer e slightly lower than those of isolate UOVS-64.2, although these yield s were similar in shake flask cultures.