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Hedman, Oleana, 2011. Hansenula anomala versus Meyerozyma guilliermondii in inhibition of Enterobacteriaceae and evaluation of maize storages in Cameroon. First cycle, G2E. Uppsala: SLU, Dept. of Microbiology



In sub-Saharan Africa post-harvest losses constitute a major problem. In order to preserve food and feed in a safe and sustainable way new methods need to be investigated and introduced. One system to preserve grain in a secure and energy saving way is by using a biocontrol organism. The yeast strain Hansenula anomala J121 is known to inhibit growth of moulds and bacteria from the Enterobacteriaceae family in stored cereal grain and is therefore regarded as a biocontrol organism.

In this study H. anomalas inhibitory effect on two Enterobacteriaceae species (Salmonella enterica serovar paratyphi B and Escherichia coli) commonly found in stored maize in Cameroon was compared with a local yeast isolate belonging to Meyerozyma guilliermondii. Maize was inoculated with H. anomala/ M. guilliermondii, H. anomala/ M. guilliermondii and E .coli/S .enterica, E. coli/S. enterica and a control with no inoculation. The maize was then put in test tubes with lids penetrated by a syringe to simulate air leakage and incubated in the dark at room temperature (25°C) for 5 ½ weeks.

No comparison could be made between the yeasts due to increases in log CFU/g maize of Enterobacteriaceae in all inoculations.

The study also explored the possibility of introducing a new storage system in Cameroon. Ten farmers in the Nforya-Bamenda (NB) area (North West region) and eight farmers in the Dschang (D) area (West region) were interviewed about their harvest, current problems during storage of maize and their openness to try a new storage system using a biocontrol organism. There were some differences in storage systems between the different areas but the most common way of preserving the maize was drying with smoke. The biggest problems in both areas were insects followed by lack of firewood in NB and transport in D. Farmers in NB were all open to try a new storage system whereas the farmers in D were more skeptical and had a lot of practical questions about the system.

During the interviews samples were taken from the farmers maize storages. The samples from NB were analyzed for the presence of Enterobacteriaceae, yeasts, moulds and total number of aerobic bacteria in order to get an overview of the hygienic status. All storages were contaminated with moulds (3.09-6.99 log CFU/g maize) and yeasts (2.96-8.38 log CFU/g maize). Plates with aerobic bacteria were smeared and most plates with substrate selective for Enterobacteriaceae had odd dilutions due to contamination. No clear CFU counts could therefore be made. The samples from D were not analyzed due to lack of time.

Main title:Hansenula anomala versus Meyerozyma guilliermondii in inhibition of Enterobacteriaceae and evaluation of maize storages in Cameroon
Authors:Hedman, Oleana
Supervisor:Olstorpe, Matilda and Niba, Aziwo
Examiner:Passoth, Volkmar
Volume/Sequential designation:UNSPECIFIED
Year of Publication:2011
Level and depth descriptor:First cycle, G2E
Student's programme affiliation:NK003 Food and Health - Bachelor's Programme, 180.0hp
Supervising department:(NL, NJ) > Dept. of Microbiology
Keywords:Hansenula anomala, Meyerozyma guilliermondii, Enterobacteriaceae, biocontrol, Cameroon
Permanent URL:
Subject. Use of subject categories until 2023-04-30.:Agricultural research
Food processing and preservation
Additional Information:The taxonomy of the different yeast species is constantly changing, Hansenula anomala has for example previously been called Pichia anomala.
Deposited On:01 Jul 2011 13:22
Metadata Last Modified:20 Apr 2012 14:21

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