Search In this Thesis
   Search In this Thesis  
العنوان
Microbiological and biochemical studies on the production of some exopolysaccharides by lactic acid bacteria and studying some of their applications \
المؤلف
Elmansy, Eman Ahmed Hassan.
هيئة الاعداد
باحث / إيمان أحمد حسن المنسى
مشرف / نجوى أحمد عبدالله محمد
مشرف / ابتسام مختار محمد القاضى
مشرف / محسن سليم عسكر
تاريخ النشر
2023.
عدد الصفحات
219 p. :
اللغة
الإنجليزية
الدرجة
الدكتوراه
التخصص
علم الأحياء الدقيقة
تاريخ الإجازة
1/1/2023
مكان الإجازة
جامعة عين شمس - كلية العلوم - الميكروبيولوجى
الفهرس
Only 14 pages are availabe for public view

from 219

from 219

Abstract

Seventeen lactic acid bacterial isolates were obtained from different food sources and selected for further studies. They grew well at 25, 35 and 40°C, but no growth was detected at 45°C except for RO30, Mpw, Mpb, and Mpx. They tolerate different salt concentrations (4.5 and 6.5 %) to a different degree; grow at different pH with optimum growth at the pH of
5.5. Also, the isolated lactic acid bacteria (LAB) showed acid and bile salt tolerance, and low hydrophobicity toward different used solvents except for Mpx and Mpb. The acid and bile salt- tolerant LAB isolates inhibited the growth of the tested pathogens and displayed varying zones of inhibition. Concerning antibiotic susceptibility, none of the isolates was susceptible to all antibiotics tested and multiple resistances were observed. Regarding exopolysaccharide (EPS) production, it was found to be ranged from 1.70±0.05 to 4.23±0.12 g/l. The isolate RO30 (from Romi cheese) was chosen for further analysis, due to its ability to produce the highest amount of EPS named REPS and its promising probiotic properties. The 16S rRNA sequencing showed it belonged to the Lactiplantibacillus plantarum group and was identified as L. plantarum RO30. REPS was constituted of glucuronic acid, mannose, glucose, and arabinose in a molar ratio of 2.2: 0.1: 0.5: 0.1, respectively.
The results of FTIR proved the existence of COO-, OH, amide
groups, and α and β-glycosidic bonds. Presence of α and β- glycosidic bonds was also confirmed by 1HNMR. The
molecular weight of REPS was 4.96×104 g/mol. In vitro, antioxidant assays proved the antioxidant potential of REPS. One factor at a time method revealed that sucrose (20 g/l), beef extract (25 g/l), and ammonium sulfate (4 g/l) increased REPS yield up to 9.11 g/l. A highly significant quadratic polynomial was obtained by the central composite design (CCD) model. The maximum amount of EPS (10.32 g/l) was produced by a combination of sucrose (40 g/l), beef extract (25 g/l), pH (5.5), incubation temperature (30 ºC), and incubation period (3 days). The healing efficacy of REPS from L. plantarum RO30 on burn wound models in albino Wistar rats showed that REPS at 0.5% concentration stimulated the process of healing burn areas indicating that the REPS might be useful as a burn healing agent in modern medicine.