Purification of Candida guilliermondii and Pichia ohmeri killer toxin as an active agent against Penicillium expansum

Abstract

An antifungal assay with cell-free culture supernatant of Pichia ohmeri 158 and Candida guilliermondii P3 was tested against Penicillium expansum strain #2 at 25°C by measuring hyphal length and percentage conidia germination. C. guilliermondii was more effective against P. expansum conidia germination (58.15% inhibition), while P. ohmeri showed higher inhibition of mycelial growth (66.17%), indicating a probable mechanism associated with killer activity. This killer toxin (molecular mass <3 kDa) was partially purified by normal phase HPLC, using TSKgel Amide-80 analytical and preparative columns. Compared with crude extract, the killer toxin eluted from the post analytical column significantly inhibited P. expansum:% inhibition rose from 42.16 to 90.93% (C. guilliermondii) and 39.32 to 91.12% (P. ohmeri) (p < 0.05). The one-step purification process was adequate in isolating killer toxin from culture supernatant and also increased anti-Penicillium activity.

Keywords:

• Penicillium expansum
• antagonist yeasts
• killer toxin
• biological control

Acknowledgements

The authors thank the CAPES Foundation-Brazil (Foundation for the Coordination of Higher Education and Graduate Training), CNPq (the Brazilian Government Organization for grant aid and fellowship to Brazilian researchers), the UGF-SETI (the Parana State-Brazil Government Secretary for grant aid), and JICA (Japan International Cooperation Agency) for financial support.