Studies On Screening, Fermentation Optimizing And Applications Of A High Pectinase-Producting Strain

The pectinase is the genaral name of enzymes that can break up the pectin. It was first extracted from oranges. The pectinase usually conclude the protopectinases, pectinlyases, polygalacturonases and pectinesterase. They are mainly from plants and animals, especially microbes. For its fast growth, simple growth condition and the special metabolic processes, microbes has become an important source of pectinase. Pectinase is well used in many fields.For example, in the fruit processing industry, pectinase can damage the stability of the suspended matter and make it condensed in the juice. So the fruit juice gets clarification and the viscosity of the juice can be reduced. In the feed manufacturing industry, it can reduce the viscosity of the feed, promote the digestion and absorption of feed in the digestive tract of animal. In the textile industry, pectinase removes most of the pectin and the waxed cotton material in the cotton fabric. In addition to this, pectinase also has an important role in woodiness anticorrosive, biological pulp, environmental protection and dirt softening industries.First, a high-producting pectinase strain was screened from sludge. It was identified as Penicillium oxalicum by morphological observation, and ITS sequence analysis. After the preliminary research, by use the orange peel and rice bran as material culture which have rich source in Zhejiang. The pectinase activity of this strain reached to18148U when ultured at the condition of28℃, pH6.0,160r/min for70h.Second, the results of the single factor experiments revealed that the optimal carbon source was orange peel powder and the best nitrogen source were rice bran and (NH4)2SO4. Then, the RSM optimization was conducted on the basis of the single factor experiments. The Regression equation Y=-460130+138200A+53266.2B+46168.1C-15247.76A2-4769.55B2-29403.7C2+960.830AB+4322.01AC-1701.47BC was established. Study results revealed that the maximum pectinase was54391.70U obtained at4.85%citrus peel powder, 5.89%rice bran,0.97%(NH4)2SO4, intial pH6.0～8.0,160r/min,9%inoculum volume and cultured at28℃for70h. Which was3times that of the initial enzyme activity.Third, The properties of pectinases from the liquid fermentation extract produced by Penicillium oxalicum were also studied. Its optimal temperature and pH were50℃and5.0respectively. The enzyme activity was stabile on30～50℃and pH5.0.Finally, the clarification of seven kinds of fruits and vegetables after processed by pectinases were studied. Through the single factor experiments, the the most clear cucumber juice obtained at2h enzymolysis time,50℃enzymolysis temperature and6%enzyme dosage. Based on this, the RSM experiments were designed with the enzymolysis temperature, time and enzyme dosage as the study of factors, the light transmittance and juice yield of vegetables and fruits as the response values. Two quadratic polynomial regression models were obtained by Response surface methodology, the lack of fits were not significant, fitting degrees were good. They can be a very good forecast for response value. Through a series of the optimization, the best technological condition for the clarification of cucumber juice processed by pectinases was:the enzymolysis time is3h, the enzymolysis temperature is42.2℃, the enzyme dosage is4.85%. In these conditions, the transmission of cucumber juice was92.12%, the rate yield of cucumber juice was93.18%.