عزل فطر الرشاشية من مصادر مختلفة ودراسة نتائج حمض الستريك بواسطة الرشاشية السوداء المعزول ومقارنته بانتاجية البكتريا اللاكتوباسلس جنسنياي

Abstract

Abstract Citric acid is very important organic acid present as intermediate in almost every metabolic respiratory mechanism .Citric acid is a tri carboxylic acid ,colorless with strong acidic taste .It is very soluble in water and insoluble in alcohol. Citric acid is produced by fungal fermentation on an industrial scale from crude sugar solutions such as molasses using Aspergillus niger by submerged fermentation. The aims of this study were: to isolate Aspergillus niger from different sources (onion , soil and orange) and to study the effect of different temperatures (28°C , 37°C and 45°C) on the colony diameter of the three isolates of Aspergillus niger up to 8 days and to study citric acid production from fungi (Aspergillus niger) and from Bacteria (lactobacillusjensenii ) and comparing between them in productivity. Using beet root substrate as sugar for Carbon source and additives (yeast extract and NaNo; as nitrogen source).Test microorganisms were: strains of Aspergillus niger which were isolated from onion ,soil (depth 15 cm)and orange and identified using Potato Dextrose Agar(PDA) medium supplemented with Rose Bengal and lactobacillusjensenii was cultured on de Man ,Rogosa &Sharpe (MRS) medium .A pure cultures of Aspergillus niger were inoculated on PDA medium and incubated at different temperatures (28°C,37°C and 45°C) .A pure culture of test microorganisms (Aspergillus niger , lactobacillus jensenii) were inoculated into different flasks containing heet + different additives separately and incubated for 10 days at 28°C (for fungus) and for overnight incubation at 37°C(for Bacteria). At 28°C the largest Aspergillus niger which isolated from onion followed by that isolated from soil followed by that isolated from orange , at 37°C colony diameter of Aspergillus niger which isolated from soil was the largest , followed by that isolated from onion, followed by that isolated from orange. Aspergillus niger at 45°C showed no growth .The production of citric acid determined by the appearance of air bubble and color's change of media and the citric acid was detected by adding Bromocryesol green indicator .Citric acid production by Aspergillus niger which isolated from the onion sample was bigger than Aspergillus niger which isolated from soil and orange . Citric acid production by lactobacillus jensenii was lower than all production by Aspergillus niger from 3 isolates .Citric acid production by addition of (yeast extract + NaNo3) to beet is high ,followed by addition of (yeast extract) ,followed by addition of (NaNo3), finally by beet only without additives .The ability of Aspergillus niger to produce citric acid was higher than production by lactabacillusjensenii .