Aim:  To investigate the microbiological and biochemical changes which occur in palm wine during the tapping of felled oil palm trees. Methods and Results:  Microbiological and biochemical contents of palm wine were determined during the tapping of felled oil palm trees for 5 weeks and also during the storage. Saccharomyces cerevisiae dominated the yeast biota and was the only species isolated in the mature samples. Lactobacillus plantarum and Leuconostoc mesenteroides were the dominated lactic acid bacteria, whilst acetic acid bacteria were isolated only after the third day when levels of alcohol had become substantial. The pH, lactic and acetic acid concentrations during the tapping were among 3·5–4·0%, 0·1–0·3% and 0·2–0·4% respectively, whilst the alcohol contents of samples collected within the day were between 1·4% and 2·82%; palm wine which had accumulated over night, 3·24% to 4·75%; and palm wine held for 24 h, over 7·0%. Conclusion:  Accumulation of alcohol in palm wine occurs in three stages during the tapping and marketing with the concurrent lactic and acetic acid fermentation taking place as well. Significance and Impact of the study:  Yeasts, lactic and acetic acid bacteria are all important in the fermentation of palm wine and influence the composition of the product.

Background B. cereus are of particular interest in food safety and public health because of their capacity to cause food spoilage and disease through the production of various toxins. The aim of this study was to determine the prevalence, virulence factor genes and antibiotic resistance profile of B. cereus sensu lato isolated from cattle grazing soils and dairy products in Ghana. A total of 114 samples made up of 25 soil collected from cattle grazing farm land, 30 raw milk, 28 nunu (yoghurt-like product) and 31 woagashie (West African soft cheese). Ninety-six B. cereus sensu lato isolates from 54 positive samples were screened by PCR for the presence of 8 enterotoxigenic genes (hblA, hblC, hblD, nheA, nheB, nheC, cytK and entFM), and one emetic gene (ces). Phenotypic resistance to 15 antibiotics were also determined for 96 B. cereus sensu lato isolates.ResultsAbout 72% (18 of 25 soil), 47% (14 of 30 raw milk), 35% (10 of 28 nunu) and 39% (12 of 31 woagashi) were positive for B. cereus sensu lato with mean counts (log10 cfu/g) of 4.2 ± 1.8, 3.3 ± 2.0, 1.8 ± 1.4 and 2.6 ± 1.8 respectively. The distribution of enterotoxigenic genes revealed that 13% (12/96 isolates) harboured all three gene encoding for haemolytic enterotoxin HBL complex genes (hblA, hblC and hblD), 25% (24/96 isolates) possessed no HBL gene, whereas 63% (60/96 isolates) possessed at least one of the three HBL genes. All three genes encoding for non-haemolytic enterotoxin (nheA, nheB and nheC) were detected in 60% (57/96) isolates, 14% (13/96) harboured only one gene, 19% (18/96) whereas 8% possessed none of the NHE genes. The detection rates of cytk, entFM, and ces genes were 75, 67 and 9% respectively. Bacillus cereus s. l. isolates were generally resistant to β-lactam antibiotics such as ampicillin (98%), oxacillin (92%), penicillin (100%), amoxicillin (100%), and cefepime (100%) but susceptible to other antibiotics tested.Conclusions Bacillus cereus s. l. is prevalent in soil, raw milk and dairy products in Ghana. However, loads are at levels considered to be safe for consumption. Various enterotoxin genes associated with virulence of B. cereus are widespread among the isolates.

The yeast populations associated with the fermentation of Ghanaian cocoa were investigated using denaturing gradient gel electrophoresis (DGGE). Samples were collected at 12-24 h intervals from heap and tray fermentations, at three different fermentation sites and different periods during the season. Eukaryotic universal primers were used to amplify a fragment of the 26S rRNA gene. The DGGE profiles were relatively complex, underlining that the fermentation of cocoa is a complex microbial process. The identities of selected fragments in the denaturing gels were revealed by sequencing. Hanseniaspora guilliermondii, Candida krusei and Pichia membranifaciens were detected from most fermentations, indicating their possible important role in the fermentation of Ghanaian cocoa. Saccharomyces cerevisiae and Candida zemplinina were almost exclusively detected during tray fermentations. The developed DGGE protocol was compared with traditional culture-based isolations. The results were comparable but slightly different, as one yeast species (C. zemplinina) was only detected using DGGE. On the other hand, Trichosporon asahii yielded only faint bands in the denaturing gels, despite the fact that it was detected using culturebased methods. Analysis of pure cultures showed that the targeted region of the 26S rRNA gene was poorly amplified in T. asahii, whereas all other investigated isolates were amplified efficiently using the chosen PCR approach. Cluster analysis revealed that the DGGE profiles clustered according to fermentation method and fermentation site. Furthermore, clustering according to progress in the fermentation was observed. The DGGE technique therefore seems to offer a relatively fast and reliable method for studying yeast population dynamics during cocoa fermentations.

Alkaline-fermented food condiments play an important role in the diets of many people in developing and a few developed countries. The rise in pH during production of these foods is due to the ability of the dominant microorganisms, Bacillus spp., to hydrolyze proteins into amino acids and ammonia. Studies have been undertaken which have investigated a number of these products like dawadawa, ugba, bikalga, kinema, natto, and thua-nao. In this review, current knowledge about the principal microbiological activities and biochemical modifications which occur during the processing of the alkaline condiments including nutritional, antimicrobial, and probiotic aspects are discussed. The current use of molecular biology methods in microbiological research has allowed unambiguous and more reliable identification of microorganisms involved in these fermentations generating sufficient knowledge for the selection of potential starter cultures for controlled and better production procedures for alkaline-fermented seeds condiments.

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