Effect of Abiotic Factors on the Antifungal Activity of Lactobacillus Strains Isolated from Commercial Dairy and Fermented Foods from Federal Capital Territory, Nigeria

Increasing consumer demand for natural products have renewed food industry attention in bio preservation. Lactic acid bacteria are of particular interest as effective alternative to chemical preservation because of their food grade status. This work explores the effect of antifungal compounds produced by isolates of Lactobacillus sp on some selected pathogenic fungi growth. Samples of diary and fermented products were purchased from commercial vendors within the Federal Capital Territory (FCT) and screened for the presence of Lactobacillus sp. The Lactobacillus sp isolated were screened for antifungal activity against Aspergillus fumigatus, Candida albicans and Trichophyton rubrum using a dual culture assay. Strains with antifungal activity were identified and the fungal inhibitory activity was further evaluated. The effect of abiotic factors on the antifungal activity was evaluated by overlay assay under different temperature and pH. Majority of the identified isolates belonged to the genus Lactobacillus. Lactobacillus sp. produced antifungal compounds under different temperatures (25ºC, 30ºC and 37ºC). The antifungal compounds produced by Lactobacillus strains showed greater inhibitory activity on Aspergillus fumigatus. At 30ºC the percentage zones of inhibition range were 44.4%- 60.4%. All isolates showed stronger antifungal activity when grown at pH 4.0 and 5.0. At a pH 2.0 there was a total inhibition of fungal growth however, there was no inhibition of fungal growth at the pH 7.0. Lactic acid bacteria can be employed as effective alternative to chemical preservatives in food. Temperature and pH of the culture medium could influence the production of antifungal compounds by lactic acid bacteria.