University of Khartoum

Detection of Proteolytic Activity of Bacillus spp. Isolated from Cooked and Raw Food in Khartoum State, Sudan

Detection of Proteolytic Activity of Bacillus spp. Isolated from Cooked and Raw Food in Khartoum State, Sudan

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Title: Detection of Proteolytic Activity of Bacillus spp. Isolated from Cooked and Raw Food in Khartoum State, Sudan
Author: Eldow, Adam Bashir Tawor
Abstract: The present study was carried out to detect the proteolytic activity of Bacillus species isolated from some sources (beef, milk, chicken, egg and rice). Period of sampling extended from 22/11/2016 to 15/1/2017. A total of fifty isolated samples were collected randomly from a public restaurants in Khartoum state, 10 samples from each source, 5 were freshly cooked (10 - 30 minute before sampling) and 5 were raw, all samples were collected as swabs, kept in plastic box with ice cubes and were sent directly to the laboratory. According to the primary and secondary biochemical tests, the total isolated Bacillus from 50 samples were 20 isolates which comprised 40% of total samples. They were Bacillus circulan 5%, Bacillus cereus 5%, Bacillus megaterium 10%, Bacillus macerans 10 %, Bacillus licheniformis 5%, Bacillus pamilus 5%, Bacillus subtilis 20%, Bacillus coagulans 15%, Bacillus laterosporus 5%, and Bacillus amyloliquefaciens 20%. The results showed that 20% of Bacillus spp. isolates were identified from boiled eggs while cooked meat isolates comprised 15% of Bacillus isolates; also 15% of isolates were found in raw milk. In addition, all cooked chicken samples were contaminated with Bacillus spp. which represented 25% of isolates. The isolates from cooked and raw rice were 25% of total isolated Bacillus. There was no growth of Bacillus spp. in raw eggs, raw meat, raw chicken, and boiled milk. The percentage in cooked samples was 80%, this was basically due to unhygienic process during and after cooking, while raw samples comprised 20% of total isolates. All isolates were motile, sugar fermenter except Bacillus cereus, and morphologically identical, but there were some biochemical variations among species such as oxidase production, most of isolates were negative except Bacillus macerans and Bacillus cereus. All isolates hydrolysed starch readily except Bacillus pamilus. Protease production was detected using milk agar medium; the most productive organism was Bacillus macerans and the lowest one was found to be Bacillus amyloliquefaciens, whereas there was no production in Bacillus circulans. Sterile chicken meat was inoculated with isolated Bacillus (B.macerans, B.coagulans, B. subtilis) in order to detect whether they actually spoil the foods. The results showed that color and consistency were changed in samples after 48 hours of incubation at 37°C, most changes occurred in samples which were inoculated with organisms with (30 mm ) and above hydrolysis zone. This study indicated that all food sources were contaminated with the genus Bacillus, indicating that Bacillus is a major source of contamination. Cooked food was more contaminated than raw food which implies unhygienic process in food cooking. The study also indicated that chicken meat was the most contaminated food compared with others. The study recommended that the workers in restaurants should be educated and instructed to care about self hygiene; also hygienic measures during and after cooking should be followed in addition to good handling of raw food during transportation and preservation.
URI: http://khartoumspace.uofk.edu/123456789/27095


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