Influence of carbohydrates on the isolation of lactic acid bacteria

AIMS: To determine the influence of carbohydrates on enrichment isolation of lactic acid bacteria from different niches. METHODS AND RESULTS: Lactic acid bacteria in three traditional fermented products in southern Africa (amasi, mahewu and tshwala) and in three fresh samples (two flowers and a fruit) were enrichment cultured in media supplemented with 13 different carbohydrates. Diversity of lactic acid bacteria was determined by PCR-denaturing-gradient gel electrophoresis. Carbohydrates used in enrichment media had a big impact on the isolation of lactic acid bacteria from fermented products. Depending on the carbohydrates tested, the number of species detected ranged from one to four in amasi, one to five in mahewu and one to three in tshwala. Fructose and mannitol selected for relatively higher numbers of lactic acid bacteria in fermented products. Specific relationships between substrates and lactic acid bacteria have been noted. On the other hand, small influences were found among carbohydrates tested in flowers and fruit. CONCLUSION: Carbohydrates have a big impact on the isolation of a variety of lactic acid bacteria in fermented food. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that reports the influence of carbohydrates on the enrichment of lactic acid bacteria.