Abstract:

The extraction conditions of konjac glucomannan by ethanol precipitation method and its antibacterial activity in vitro have been studied with the konjac powder used as raw material.The effects of the solid to liquid ratio,pulp temperature,ethanol concentration and washing times on the yield of konjac glucomannan were firstly studied through single factor experiements.And then,the optimum extraction conditions were obtained through orthogonal experiment.Lastly,in vitro antibacterial activity of konjac glucomannan was determination by the tube double gradient dilution method.The results showed that the optimum extraction conditions of konjac glucomannan were as follows:solid to liquid ratio was 1∶175 （g∶mL）,pulp temperature was 60 ℃,the ethanol concentration was 50%（v/v）,and twice washing.In these conditions,the konjac glucomannan rate reached 65.7%.The konjac glucomannan showed different levels of inhibition for staphylococcus aureus and escherichia coli.It is then concluded that konjac is rich in glucomannan and it has the antibacterial activity,which makes it widely applicable in medicine and food industry.

Key words: konjac glucomannan, ethanol precipitation method, antibacterial activity