Effect of chemical, physical and enzymatic treatments on Lactococcus lactis' surface agglutinin and its precipitating ability

The precipitating proterty of Lactococcus lactis agglutinin has a negative effect on yield of starch and expanded delaminating time during Chinese traditional mung bean starch processing; thus, it is of interest to find a way to destroy the precipitating property of the agglutinin. In the present study, L. lactis isolated from sour liquid was treated with chemical, physical, and enzymatic methods, respectively. It was found that 12.0-13.7 mol/L of ethanol or 12.3 mol/L of hydrogen peroxide or 0.1 mol/L of HCl, or 0.1 of mol/L NaOH or 0.3 mol/L trichloroacetic acid could destroy the ability of the agglutinin from L. lactis to precipitate starch and expand delaminating time significantly. Periodic acid sodium which destroys the structure of glycosyl also made L. lactis lose its agglutinin activity and precipitating ability. Similarly, pepsin and trypsin had the same function as periodic acid sodium did. The present study might provide a good way to increase the starch yield and delaminating time during the mung bean processing. PRACTICAL APPLICATIONS Sour liquid processing has been used for hundreds of years to produce mung bean starch in China because this kind of starch had better quality than that from other processing methods. However, this processing consumed a lot of water while producing a large amount of waste water, resulting in environmental pollution. Many scientists considered that Lactococcus lactis in sour liquid is the main factor to precipitate starch. The agglutinin on the surface of L. lactis is directly involved in starch deposition. Therefore, our research focuses on improvement of starch yield by using L. lactis-immobilized columns through which starch slurry passes. This technology will cut down waste water and meet the national requirements, so that we do not doubt the prospect of the technology. To develop this technology, we should learn what kinds of factors will affect the precipitating ability of agglutinin of L. lactis. This manuscript reports a study on how chemical, physical and enzymatic substance can affect the precipitating ability of agglutinin.