从实验室保藏菌株中筛选出1株果糖转化率高的乳酸菌并进行菌种鉴定,探究其利用菊糖酶解液制备L-乳酸的发酵工艺参数。从4株乳酸菌中筛选获得1株高产L-乳酸的菌株(编号zh),经形态观察和基因序列分析,该菌株为植物乳杆菌(Lactobacillus plantarum)。采用单因素试验考察影响该菌株乳酸发酵的培养基质和条件,确定影响L-乳酸产量的主要因素为MnSO4、NaAc、培养温度、pH值,经正交试验优化,所得最佳发酵条件为MnSO4 0.6 g/L、NaAc 7 g/L、培养温度34 ℃、pH值4。在此条件下L-乳酸产量可达14.37 g/100g(菊芋干粉),该值与模型预测值(13.99 g/100g)吻合,说明所建立模型切实可行。该工艺为利用非粮原料菊芋制备L-乳酸提供科学依据。
A lactic acid bacteria (No.zh) with high fructose conversion rate was screened from the strain reserve in our laboratory and its species name was identified.The fermentation parameters of producing L-lactic acid from inulin hydrolysate of strain zh were investigated.The strain zh was identified as Lactobacillus plantarum based on its morphological features,physiological and biochemical properties,as well as 16S rDNA sequence analysis.According to the single factor experiments of medium formula and culture conditions,the main factors affecting L-lactic acid production were MnSO4,sodium acetate,culture temperature and pH.The orthogonal experimental design was employed to optimize the process parameters of L-lactic acid fermentation from inulin hydrolysate.The optimal fermentation conditions were MnSO4 0.6g/L,sodium acetate 7g/L,initial pH 4.0,incubation temperature 34 ℃.Under these conditions,the yield of L-lactic acid was up to 14.37 g/100g (inulin),which was consistent with the predicted value (13.99 g/100g).These findings suggest that this technology has potential application for preparing L-lactic acid from non-grain starch-containing feedstock Jerusalem artichoke.
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