Breeding Of Gibberellic Acid Overproducting Strain And Fermentation

Gbberellins have been applied more and more in agriculture, which are a large familyof natural plant hormones. The commercial bio-active GAs, particularly gibberellic acid(GA₃), are produced by fermentation of the fungus, Gibberella fujikuroi. Nowadaysmany researches are focused on breeding high-producing strains and optimizingfermentation technology. In this paper, improving product of GA₃ via three ways.1. Studies on the mutant breeding of high-yield gibberellins strainThe protoplast of Gibberella fujikuroi m978 were treated by mutation breeding forhigh-yield gibberellins, LiCl mutation was better than DES mutation or UV irradiation ifsingle mutation, but any single mutation was worse than compound mutation by whichthe mutants were more overproducting and genetically stable. So compound mutation isan effective method for genetic breedings.Making use of lipase activity as marker, the soybean oil tolerant mutants were screenedby compound mutation and natural selection , and a high-titer mutant mFH-420 wasobtained whose potency was increased by 38.8% over the parent strain.2. Study of Construction on genic engineering strain expressing VhbThe trpC promoter gene (PtrpC) and Vitreoscilla hemoglobin gene (vgb) weregenerated by PCR from plasmid pSKH and pBMB666, then PtrpC-vgb gene was placedvia SOE-PCR(Splicing by overlap extension PCR).Recombinant plasmid ofAgrobacterium tumefaciens, pMELZ002, was constructed,which had PtrpC-vgb geneand hygromycin B resistance gene (hph). The gene fragment could be efficientlytransferred to chromosome of Gibberella fujikuroi m978 by the aid of T-DNA ofAgrobacterium tumefaciens EHA105.Six transformats were isolated, of which PCR analysis indicated vgb gene had beenintergrated into chromosome. CO binding difference spectrum revealed that vgb gene hasbeen expressed successfully in transformat M-32, and the fermentation results showedthat expression of vgb gene could promote GA₃.The paper is beneficial to molecularbiological research and genetic modification of Gibberella fujikuroi.3. Effects of plant oils on the ferment of Gibberellin Acid and its analysisVarious plant oils increased the production of Gibberellin Acid by Gibberella fujikuroimutant m143. Maximum titer of Gibberellin Acidin media containing sesame, soybean,Olive oils and dextrose were 1480, 1300, 1250, 890μg/mL.Fatty acids of plant oils may stimulate Gibberellin Acid accumulation while glycerolcomponent had no the function. Some minim elements of plant oils could influence theferment, e.g. sesamol of sesame oil.