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In order to screen antifungal activity of lactobacilli that produce bacteriocin against the yeast Candida, ninety-two food and clinical samples were collected. Also, several commercial brands of Lactobacillus probiotics and ready-made isolates of Lactobacillus were used. The isolated lactobacilli were subjected to microscopic, macroscopic, and biochemical tests. Moreover, molecular identification was performed for the best producer isolate. For Candida spp. isolation, seventy- two samples were collected from different clinical sources; in addition, nine of ready-made isolates were also used. All the isolated Candida spp. were subjected to microscopic and macroscopic examinations which were confirmed by VITEK® 2 YST card automated system. Detection of bacteriocin production from Lactobacillus was investigated by primary and secondary screening techniques and the results showed that the agar wells diffusion method was the best. The most efficient isolate to produce bacteriocin was L. plantarum WZD3, in which antifungal activity of bacteriocin was at the level of 80 and 40 AU/ml against the most sensitive Candida isolates; C. albicans CA and C. albicans CB, respectively. After partial purification of bacteriocin by n-butanol extraction method, bacteriocin activity was increased to 320 AU/ml against both yeast isolates. In conclusion, L. plantarum WZD3 or its bacteriocin could be a good candidate as antifungal agent to treat Candida infections and more studies are required to evaluate its acivity against other types of medical fungi.

For partial purification of plantaricin WZD3, a bacteriocin produced by Lactobacillus plantarum WZD3 which has antifungal activity against Candida albicans, three procedures were performed; adsorption-desorption method, coldacetone extraction method and n-butanol extraction method. The results showed that n-butanol extraction method was the best since the activity of bacteriocin increased to 320 AU/ml. Characterization of plantaricin WZD3were also studied and the results showed that this bacteriocin have high thermostability at different temperatures, it remained active without losing its activity after being treated with (20-80) °C for (10, 30 and 60) minutes, but it retained only 50% of its activity after treatment at 100°C at the same periods of exposure and at 121°C for 15 minutes. Also, the activity of bacteriocin was stable at pH values (4-7) while at the pH values (8-11), the antifungal activity was decreased to the half, on the other hand, complete loss of activity was observed at pH (2, 3 and 12). Antifungal activity of plantaricin WZD3 was disappeared when it treated with proteolytic enzymes (pepsin and trypsin), whereas it retained whole activity when treated with lysozyme and α-amylase, indicating pure proteinaceous nature of it. The results of effect of storage period revealed that the activity of plantaricin WZD3 was gradually decreased during storage. In conclusion, plantaricin WZD3 could be a good candidate as antifungal agent and its properties are promising to use it as biopreservative instead of chemicals preservatives.

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Bacteria could produce bacterial nanocellulose through a procedure steps: polymerization and crystallization, that occur in the cytoplasm of the bacteria, the residues of glucose polymerize to (β-1,4) lineal glucan chains that produced from bacterial cell extracellularly, these lineal glucan are converted to microfbrils, after that these microfbrils collected together to shape very pure three dimensional pored net. It could be obtained a pure cellulose that created by some M.O, from the one of the active producer organism like Acetic acid bacteria (AAB), that it is a gram -ve, motile and live in aerobic condition. The bacterial nanocellulose (BNC) have great consideration in many fields because of its flexible properties, features and advantages of the BNC. So in this study, the acetic acid bacteria (5AC) isolate was isolated from apple vinegar and detected the ability of this isolate to produce the nanocellulose on the Hestrin-Schramm (HS) medium, and then optimized the production condition, four parameters were investigated: temperature, pH, different carbon sources and nitrogen sources.  After incubation the isolate for about (168- 192) hrs, the highest yield of BNC was identified by determining the wet weight, dry weight also the consumed sugar for each parameter.

Bacteriocin produced by Lactobacillus acidophilus was partially purified by ammonium sulfate precipitation 60% saturation. The bacteriocin exhibited activity of 320AU/ml against Serratia marcescens. Characterization of bacteriocin showed that its active principle was proteinaceous in nature since it was inactivated by proteolytic enzymes but not by other enzymes. Treatment of bacteriocin with organic solvents 5% concentration did not affect the activity of it, but its activity was reduced to the half at 10% concentration of the solvents. Bacteriocin activity was stable at pH 4 -7, half of its activity was lost at pH8, and whole activity was lost at other pH values. Bacteriocin was stable at 40-100°C for 10min, but it retained only 50% of its activity at 40 and 60°C for 30min. whole activity was lost at 80 and 100°C for 30min and at 121°C for 15 min.