Microbial is a renewable resource which can produce polysaccharide. Its unique physiological activities and broad applications are attracting increasing attention. In this article, the source and the fermenta- tion conditions of microbial polysaccharide was reviewed, with a view to provide a scientific basis for the production of the microbial polysaccharide.

Objective To investigate the effectivity of bispectral index(BIS)and auditory -evoked potentials index(AEP index)in monitoring the depth of desflurane anesthesia in the elderly. Methods Sixty patients(ASA gradeⅠ～Ⅱ)without obvious auditory and psychiatric dysfunction undergoing general anesthesia were enrolled in this study,and they were devided into the elderly group (n=30)and the non-elderly group(n=30)according to the age.After the endotracheal intubation,the lungs were ventilated with desflurane in oxygen.End-tidal concentrations of desflurane were maintained at 0.6,1.0 minimum alveolar concentrations(MAC)and 1.3 MAC for 20 minutes, respectively.The changes of BIS,AEP index,mean arterial blood pressure(MAP)and heart rate (HR)were recorded simultaneously.Results In the elderly and non-elderly groups,BIS were 94.14?6.5 and 94.5?4.6(P＞0.05),and AEP index at pre-anesthesia were 87.2?11.7 and 89.2?6.9(P＞0.05)respectively,which showed no statistic difference between two groups.BIS and AEP index decreased significantly in each time point at pre-anesthesia compared with those during anesthesia in two groups (P＜0.05).In the periods of increasing concentration of desflurane,BIS decreased gradually in two groups(P＞0.05),but BIS in the elderly group were higher than in the non-elderly group at the same end-tidal desflurane concentration(P＞0.05),and BIS negatively correlated with the end-tidal desflurane concentration in two groups.In the elderly group,AEP index decreased significantly at the concentration of 1.0 MAC and 1.3 MAC of desflurane compared with that of 0.6 MAC(P＜0.05),but there was no difference in AEP index with increasing end-tidal desflurane concentration from 1.0 MAC to 1.3 MAC(P＞0.05).At every concentration of desflurane,AEPindexintheelderlygroupwaslessthaninthenon-elderlygroup(P＜0.05).Conclusions BIS and AEP indexes correlate well with the end-tidal desflurane concentration,and are valuable for monitoring the depth of desflurane anesthesia in the elderly.AEP index can predict the difference in depth of anesthesia at the same end-tidal desflurane concentration between the elderly and the non-elderly.