Study On The Formentation Conditions Of Gibberellins Produced By The Strain SFGi-1

As a kind of natural regulator of plant growth, gibberellins were applied widely in agriculture. Currently, industrial production of gibberellins mostly fermented by Gibberella fujikuroi. So, study on the production technics of gibberellins produced by mould has profound significance. Generally, there are two ways to improve the production of gibberellins: improving the fermentation potency of gibberellins through breeding high-producing strains or optimizing culture conditions; maximizing extraction efficiency of gibberellins by adjusting extracting process. In this paper, we studied the fermentation conditions of Gibberella fujikuroi SFGi-1 preservated by our laboratory and the extraction conditions of gibberellins .The main results were as follows:The culture medium and the fermentation conditions of the strain SFGi-1 producing gibberellins were optimized by the experiment. The optimum culture medium was: 100g/L starch, 15g/L peanut meal, 3g/L soybean meal, 0.75g/L magnesium sulfate, 1g/L potassium dihydrogen phosphate. Adding 0.2g/L cobalt chloride and 0.5g/L citrate into culture medium benefited to gibberellins synthesis. The suitable culture conditions were as follows: initial pH 5.5, temperature 30℃, rotation speed of rocking bed 180r/min, broth's volume in shake flask 35mL/250mL, inoculation amount 5%. Under the optimum condition, the production of gibberellins achieved 1424mg/L , it was 5.6 times more than the value to the initial.The solid fermentation conditions of the strain SFGi-1 were studied. Two more suitable solid fermentation culture medium were determined:(1)50% wheat bran, 50% corn meal, 0.1% potassium dihydrogen phosphate, 0.1% magnesium sulfate,1% glucose. The production of gibberellins was 6358mg/kg by cultivating twelve days in this culture medium under 30℃.(2)Rice medium: rice, 4% peanut meal, 0.1% potassium dihydrogen phosphate, 0.1% magnesium sulfate. The production of gibberellins reached 7982mg/kg by cultivating twelve days in this culture medium under 30℃. The extraction conditions of gibberellins from culture were studied. The appropriate extraction conditions of gibberellins from solid culture were as follows: solid culture was doused by water in order to extract gibberellins , the water adding proportion was 1:6, the extraction time was 5 hours.The extraction of gibberellins from fermentation broth adopted solvent extraction. It mainly contained acidizing filtration, diatomite aid filtration, activated carbon decolorizing, extracting with ethyl acetate . The suitable conditions of extracting with ethyl acetate was: pH2.0, extracting temperature was 30℃, the ethyl acetate extracting time was two times, the amount of ethyl acetate for one time was equal to amount of fermentation broth. The recovery ratio of gibberellins by the method achieved 75.8%.In this thesis, the fermentation conditions of the strain SFGi-1 producing gibberellins were optimized and the extraction conditions of gibberellins from culture were determined. It laid a foundation for the further study of GAs production.