响应面法优化胶红酵母伴生的维生素C混菌发酵培养基

Optimization of Medium by Response Surface Methodology for Vitamin C Mixed Culture Fermentation with A New Companion Strain Rhodotorula mucilaginosa

从沈阳东陵龙尾湖淤泥中,筛选分离到一株具有促进维生素C(VC)混菌发酵中产酸菌K.vulgare产酸的新伴生菌A8,对菌株A8核糖体ITS rDNA进行PCR扩增并测序,获得长度为610 bp的ITS rDNA序列。在NCBI数据库上进行同源性比对,构建ITS rDNA系统发育树,并进行系统发育分析,再结合形态学鉴定,确认菌株A8为胶红酵母菌(Rhodotorula mucilaginosa)。该菌与K.vulgare组成VC混菌发酵新菌系,产2-酮基-L-古龙酸(2-KGA)量高达52.56 g/L。在单因素试验基础上,采用响应面法对发酵培养基成分进行优化,得到最佳培养基条件为:L-山梨糖80 g/L、尿素14 g/L、玉米浆15 g/L、CaCO31.58 g/L、MgSO40.3 g/L、KH2PO41.0 g/L。在优化条件下发酵,可使2-KGA产量达70.08 g/L,与理论值70.38 g/L基本一致,转化率达81.3%。优化后的培养基比原培养基平均提高2-KGA产量17.52 g/L,表明新筛选的胶红酵母菌具有较强促产酸的伴生能力,并且该菌在通常情况下对动物和人体不致病,为工业生产提供重要的伴生菌资源。

A new company strain of A8,which can promote 2-keto-L-gulonic acid(2-KGA)produced by K.vulgare in vitamin C(VC)mixed culture fermentation,was separated from the source of Longwei Lake silt,Dongling Shenyang.The ITS rDNA was amplified by PCR and sequenced to obtain a 610 bp ITS rDNA.Analysis was performed by homology comparison with the NCBI database to construct the phylogenetic tree basing on ITS rDNA sequences.And the strain of A8 was determined as Rhodotorula mucilaginosa based on the molecular identification combining with morphological identification.The R.mucilaginosa and K.vulgare composed of a new mixed culture of VC fermentation system and the production yield of 2-KGA was 52.56 g/L.Based on single factor tests,the components of fermentation medium were optimized by response surface methodology(RSM).The optimal culture conditions were as follows:80 g/L L-sobose,14 g/L urea,15 g/L corn liquor,1.58 g/L CaCO3,0.3 g/L MgSO4 and 1 g/L KH2PO4.The yield of 2-keto-L-gulonic acid was up to 70.08 g/L under the optimal medium in VC fermentation,which is consistent with the theoretical value of 70.38 g/L and the conversion rate was 81.3%.The average yield of 2-KGA was increased to 17.52 g/L with the optimized medium more than with the original medium,suggesting that the R.mucilaginosa have the companying ability to K.vulgare for promoting 2-KGA production.In addition,R.mucilaginosa is not pathogenic to animals and human body in normal conditions,which can be used as a new company strain for VC industrial production.