Isolation and Screening of bacteriocin producing lactic acid bacteria from milk and milk products

One of the most important groups of acid producing bacteria in food industry is the lactic acid bacteria,(LAB). LAB are widespread in nature and predominate in microflora of milk and its products LAB are known to produce bacteriocin and have great potential in food bio preservatives. In the present study a total of 160 strains of LAB were isolated from eight different milk and milk products collected from Dairy Farm, Annamalai University. They were screened for the production of bacteriocin active against Listeria monocytogenes. Among the 160 strains 22 strains were observed as positive bacteriocin producers. The highest percent (25.0%) of bacteriocin producers was recorded in butter followed by yoghurt (20%), curd (18.75%) buffalo milk (16.66%), Goat milk (13.88%) Cheese (11.11%) cow milk (10%) and dairy milk (6.25%). The bacteriocin producers were identified upto generic level as Enterococcus, Lactococcus, Lactobacillus and Streptococcus.  There was a striking predominance of  the genus Enterococcus (55%) followed by Lactococcus (22%) in the milk and milk products. The spectrum of inhibitory activity of the bacteriocin producers against Gram positive and Gram negative pathogens were tested and observed that, activity is restricted to Gram positive organisms, but Lactobacillus and Streptococcus were active against both Gram positive and Gram negative organisms. The bacteriocins produced by LAB are to be characterized in the further studies

Fungal Decolourization of Direct Azo Dyes and Biodegradation of Textile Dye Effluent

AbstractDecolourization of Direct azo dyes by fungi isolated from textile dye effluent was investigated. Seven different fungal species were isolated and identified. The fungal isolates were identified as Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Fusarium oxysporum, Penicillium chrysogenum, Mucor sp. and Trichoderma viride. The fungal inoculums were inoculated into flasks containing Direct azo dyes (500 mg/l) with trace amounts of yeast extract, glucose and sucrose and then sterilized and incubated for 12 days. Aspergillus niger completely decolourized the Congo Red within 6 days. The best decolourizer of Viscose Orange-A was Aspergillus fumigatus (88.70%). Mucor sp. (69.73%) was identified as the best decolourizer of Direct Green – PLS. The dye Direct Violet-BL was completely decolourized by Aspergillus niger within 9 days and Trichoderma viride within 12 days. The dye Direct Sky Blue-FF was completely decolourized by Aspergillus flavus within 9 days and Mucor sp. within 12 days. Penicillium chrysogenum have the capacity to completely decolourized the dye Direct Black-E within 12 days. Fungal biodegradation was assessed by physicochemical analysis