الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The probiotic bacteria enhance a favorable impact on the host by improving the intestinal microbial balance and moderate digestive disorders. They simplify a good environment for the smooth functioning of various metabolic activities which are due to the bioactive compounds production. The bioactive compounds produced by these bacteria include bacteriocins, enzymes, vitamins, amino acids, oligosaccharides, exopolysaccharides, short-chain fatty acids and immunomodulatory compounds. Due to the action of acids by changing the pH and reducing the oxygen availability and proteolytic activity of lactic acid bacteria the intestinal pathogenic organisms are suppressed
Moreover, the beneficial effects of probiotics, the production of antimicrobial substances, stimulation of mucus secretion and dendritic cell maturation, an improvement of gut mucosal barrier function, and modulation of host gene expression. Importantly, probiotics have been proven to be able to revert intestinal dysbiosis, which may play a role in the development of several degenerative diseases, as well as chronic diseases, including cancer. A growing amount of clinical studies are currently investigating the impact of probiotics on the treatment of intestinal toxicity during chemotherapy, immunotherapy and radiation, generating promising results.
Soymilk is aqueous extract of soybean it is not widely accepted by consumers due to dislike flavor, often described as “beany” . Fermentation by probiotic bacteria may be reduced the beany flavor caused by lipoxygenase activity, and lowering acceptability of soymilk. Soy yoghurt is a fermented soymilk made with a mixed starter culture consisting of Streptococcus thermophilus and Lactobacillus sp. Fermenting soymilk with probiotic lactic acid bacteria considerably increases its health value. Due to a greater antioxidative actions, they are considered healthier than pure soymilk.
The content of the oligosaccharides, namely verbascose, stachyose and raffinose, which cause flatulence, also lowers by fermentation with probiotic bacteria. Fermented soymilk is easily digestible and has antioxidant properties that prevent cancer This may be because of the β-galactosidase activity improvement which converting isoflavone glycosides towards aglycones, the latter are the bioactive forms known for their health benefits .
Aim of study
To produce fermented soymilk by probiotic bacteria (lactic acid bacteria and bifidobacteria) and shortening the fermentation time. Then use this milk with a high nutritional, health and economic value as a substitute for fermented dairy for helping some people who are lactose intolerance and allergic to milk proteins.
Results could be summarized in the following points:
1- Five probiotic bacterial strains (Lactobacillus plantarum, L. casei, L. acidophilus Lactococcus thermophilus and Bifidobacterium longum) used for soymilk fermentation these strain were collected from the Food Technology Research Institute, Agriculture Research center in Giza, Egypt. These strains have been used as a single and consortia to ferment soymilk.
2- These strains cultivated in soymilk During the 12 h fermentation period the samples were taken every 2 hours. Results show that there was a significant increase in The bacterial viability or the viability of inoculum in fermented soymilk (soy yogurt) increased from 3.20 to 9.98 Log CFU/mL.
3- pH decreased from 7.20 to 4.38, while TA increased from 0.01% to 2.03% for soymilk fermented.
4- The chemical composition of soymilk fermented by probiotic bacteria was determined, the total solids, protein, and ash content were increased, while a decrease in moisture, fat and carbohydrates contents was observed, when compared with non-fermented one.
5- the antioxidant properties of fermented and non-fermented soymilk products was determined by DPPH radical antioxidant activity in DPPH radical-scavenging (ranging from 26 to 80 %) as compared to that unfermented soymilk (1%). Result also exhibited that the treatments extracted by ethanol were favored as antioxidant activity than extracted by water. The maximum significantly antioxidant activity was noticed by C18 showing 79.9, and 80%, while C5 shown the lowest one.
6- Seven pathogenic bacterial strains were obtained from Agricultural Microbiology Department, Faculty of Agriculture, Ain Shams University, Shoubra, Cairo, Egypt. These bacteria included Escherichia coli O157H7, Shigella shag As2, Salmonella typhimirium As3, Staphylococcus aureus As4, Bacillus cereus Dsmz345, Pseudomonas aeruginosa Atoc27853 and Listeria monocytogenes As1. All these strains were used to investigate antimicrobial activity. E. coli O157H7 being the most sensitive strain, which recorded the largest diameter (DIZ) with 8 selected probiotic bacterial cultures as a single and co-cultures ranged from 20mm, 19mm, 10mm, 20mm, 22mm, 19mm, 17mm, and 15 respectively.
Gram-negative pathogenesis was more significantly sensitive to probiotic cultures than gram-positive pathogenesis, All tested probiotic cultures had more significant antibacterial activity against E. coli O15H7, S. typhimirium As3, and Shigella shigae As2 which gave inhibition zone diameter (IZA) ranged from 10 to 20 mm, 12 to 16 mm, and 10 to 16 mm, respectively. The most significant probiotic cultures were appeared high antibacterial activity against the tested pathogens being C18, C8, and C1. The co-culture of L. plantarum+L. thermophilus+B. longum (C18) fermented soymilk gave the highest IZD toward E. coli O15H7 (22 mm), Shigella shigae As2 (17 mm), S. typhimirium As3 (16 mm), S. aureus As4 (15 mm), L. monocytogenes (13 mm), and B. cereus Dsmz345 (12 mm) while, the lowest IZA was observed by P. aeruginosa (8 mm).
7- Minimum inhibitory concentration (MIC) value of three treatments of fermented soymilk cultures against 7 tested pathogenic bacterial cultures after 24 h of incubation period, The MIC values of the tested fermented soymilk cultures was found at dilution ranged between 3.72 and 2.11 CFU/mL (0.25 and 0.125 dilutions), respectively. Gram- negative bacteria of E. coli, shigella sp, and S. typhi observed to susceptible for all fermented soymilk cultures treatments (T1, T2, and T3) at MIC value of 2.11 CFU/mL (0.125 dilution) expect P. aeruginosa which sensitive at MIC value of 3.72 CFU/mL (0.25 dilution). Whereas Gram- positive bacteria of S. aureus, Bacillus cereus, and L. monocytogenes were appeared sensitive to T1 (L. planterium ATCC14917 C1) at MIC value of 3.17 CFU/mL (0.25 dilution) and to T2 (L. plantarum ATCC14917 + L. thermophiles) and T3 (L. plantarum + Lc.thermophilus DSM20259 +B.longum B41409) at MIC value of 2.11 CFU/mL (0.125 dilution).
8- Minimum bactericidal effects with different value in all tested fermented soymilk samples. Results in Table (11) showed that MBC value at dilutions ranged between 1 and 0.125 (9.98 and 3.72CFU/mL). In case of Gram-negative bacterial pathogenic, E. coli, shigella, and S. typhi were appeared sensitive to T1 and both T2 and T3 at MBC of 9.98 and 2.11 CFU/mL (1.0 and 0.125 dilutions), respectively. In case of Gram-positive bacterial pathogenic, S. aureus, and L. monocytogene had sensitive to T1, and T2 at MBC of 9.47and 2.11 CFU/mL (1.0 and 0.5 dilutions), respectively. While B. cereus had sensitive to T1 and both T2 and T3 at 9.98and 2.11CFU/mL (1.0 and 0.25 dilutions) of MBC, respectively.
Revealed that the tested fermented cultures had bactericidal effect with MBC / MIC ratio ≤ 2 against 4 pathogenic strains out of 7 strains in case of T1 (L. planterium ATCC14917 C1) and T2 L. plantarum ATCC14917+ Lc. thermophiles DSM20259 (C8), and against 5 strains in case of T3 (L. plantarum + Lc. thermophilus DSM20259 +B.longum B41409 C18).
Moreover, all fermented cultures also appeared bacteriostatic effect (MBC / MIC ratio ≥ 4) against both S. aureus, P. aeruginosa ATCC27853 as well as, Bacillus cereus, and L. monocytogenes in the case of T1 and T2, respectively.
9- Results cleared that the three treatment of probiotic bacterial cultures had a bactericidal and bacteriostatic effect against both (Gr+ve bacteria) and (Gr -ve bacteria), all probiotic cultures had a bactericidal effect against E. coli O15H7, S. typhimirium As3 and, S. shigae As2, T1 and T3 had a bactericidal effect against L. monocytogenes, T2 and T3 had a bactericidal effect against B. cereus. While all three probiotic cultures had a bacteriostatic effect against S. aureus As4 and P. aeruginosa ATCC27853 in addition to T2 had a bacteriostatic effect against L. monocytogenes, and T1 had a bacteriostatic effect against B. cereus Dsmz345.
10- The previous experimental results shown that C18 was the most significant probiotic cultures used for soymilk fermentation, response surface methodology (RSM), was used to select the best conditions for soymilk fermentation, Seven different variables were selected to perform this optimization process, incubation period, inoculum size, temperature, pH, sodium citrate, stevia, and chitosan polymer. This variables at the same time set in 16 experimental runs to maximize fermentation of soymilk by C18, the viable cell count, pH, total acidity, and coagulation time was measured, the most three significant variables affected on soymilk fermentation incubation time (A), temperature (C), and pH (D). the run number 9 shown the best results, pH=4.37, TA=1.98, viability= 9.98, and coagulation time= 5.20, after selecting the most significant variables a central composite design (CCD) was performed to determine the optimal levels of the selected significant variables, 20 experiments with different combination of incubation period (A), pH (B), and incubation temperature (C) for improvement of total acidity, viability, and coagulation time of fermented soymilk. The maximum values of viability (9.98 CFU/mL) and total acidity (2.25%) were achieved at run number 1 after adjusted pH to 7.2 and incubated at 37 °C for 8 h of fermentation time, respectively. The coagulation time of this run was 5.30 h.
11- The toxicity experiment was done In vivo Sprague dawley rats were divided into three group, group one was the control group, group two refer to the rats were feed fermented soymilk, and group three were feed commercial yoghurt, at the end of this experiment, no significant results shown any changes in body weight, organs weight, biochemical analysis, and histological analysis of liver, kidney, and spleen.
12- Antidiabetic properties of fermented soymilk was determined In vivo Sprague dawley rats were divided into four group, group one, negative control group, group2 positive control group, group3 fermented soymilk treated group, and group4 commercial yoghurt treated group, from this experiment, FSM, and CY shown a antidiabetic properties.
13- Anticancer properties of FSM, qin this experiment two type of caner cell was obtained and treated with FSM, from this experiment the cancer cell was inhibited with FSM, and FSM shown an anticancer properties.
14- Finally, shelf-life (storage period) was studied, this experiment shown that FSM able to save its properties during storage period, and viability still above. (106 CFu/ml) which would be stable during 28-day cool storage, that is the requirement for probiotic foods.