Biocontrol efficacy of Wickerhamomyces anomalus in moist maize storage

Abstract

White maize cultivar ‘Kasai’ was harvested and stored moist, sealed in airtight plastic barrels, with and without inoculation of the biocontrol yeast, Wickerhamomyces anomalus. Microbes were enumerated at harvest and after 2, 5 and 8 months of storage. Moist storage of maize yielded a type of fermentation, in which high levels of lactic acid bacteria (LAB) naturally present on maize (108 cfu/g), were maintained throughout storage. Activity of LAB in both control and inoculated maize likely contributed to the decline in Enterobacteriaceae to < 10 cfu/g after 2 months storage, a good outcome for food and feed hygiene. The biocontrol yeast, W. anomalus, appeared to have died out in the inoculated treatment after 2 months; nevertheless, a positive effect was seen in significantly reduced mould counts to < 100 cfu/g compared with the uninoculated maize. Reducing moulds during storage minimises the risk for mycotoxin production. Storage for 8 months with the biocontrol yeast did not appear to affect nutritional parameters of the maize, such as dry matter, crude protein and total amino acids. Compared with the uninoculated control, inoculated maize had significantly better contents of three amino acids (alanine, aspartic acid and glycine), but poorer contents of six amino acids (arginine, lysine, ornithine, proline, serine and tyrosine). The absence of nutritional improvement in inoculated maize could be due to the poor survival of the biocontrol yeast, and altered formulation practices may address this. 

Keywords: Feed hygiene, microorganisms, storage, maize, Wickerhamomyces anomalus, biocontrol.

African Journal of Biotechnology, Vol 13(44) 4208-4214