| Eurycoma longifolia Jack is a perennial shrub plant grown in Southeast Asian countries and has high medicinal values.However,E.longifolia plant material is not sufficient for meeting the market demand because of the excessively excavated wild resource and a long cultivation period.The bioreactor culture technology is an effective approach to rapidly mass production of alternative plant materials such as cells or organs.At present,studies on the bioreactor adventitious root（AR）culture for the production of the main bioactive compounds of E.longifolia（i.e.,polysaccharides and eurycomanone）are lacking.Therefore,this study investigated the effects of several factors affecting AR growth and accumulation of polysaccharides and eurycomanone to establish bioreactor culture system of E.longifolia ARs.For the AR utilization in the production of antibacterial related products,this study used different AR extracts to explore the antibacterial activity.In this study,a 5 L bioreactor culture was used to investigated the effects of sucrose concentration in the medium,inoculation density and aeration rate on adventitious root growth and accumulation of polysaccharides and eurycomanone.The dynamic study of AR growth and bioactive compound synthesis were also implemented for selection of a suitable culture period.The results showed that among sucrose concentrations from 30 g·L-1to 60 g·L-1,the favorable AR biomass and polysaccharides and eurycomanone content were found in the group of 40 g·L-1sucrose.The inoculation density obviously affected AR culture efficiency,5 g·L-1of inoculation density was the most optimal compared with inoculation densities of 2.5,7.5,and 10 g·L-1.The aeration rate from 0.05 vvm to 0.125 vvm exerted different culture efficiency,the highest AR biomass and contents of polysaccharides and eurycomanone were determined in the group of 0.05 vvm aeration rate.The dynamic study indicated that the maximum AR biomass accumulation and bioactive compound contents were on day 40 of culture,at the time,AR fresh weight and dry weight reached 279 g and 28 g per a bioreactor,respectively,and the contents of polysaccharides and eurycomanone reached 359.89 mg·g-1and 1.32 mg·g-1,respectively.In experiments of antibacterial activities,crude extract（CE）of ARs and the fractions from extraction using different solvents（petroleum ether extract,dichloromethane extract,ethyl acetate extract,n-butyl alcohol extract,water）exhibited different antibacterial effects against Escherichia coli,Bacillus subtilis,Staphylococcus aureus,and Pseudomonas aeruginosa.Antibacterial effect of CE on Bacillus subtilis(MIC=2 mg m L-1)was better compared that of other tested bacterial species.Among five fractions of extracts,the dichloromethane fraction（DCM）effectively inhibited B.subtilis(MIC=1 mg m L-1)and S.aureus(MIC=0.25 mg m L-1)growth.After CE and DCM treatments,the alkaline phosphatase,electrolytes,nucleic acids,and proteins obviously leaked out from cells of B.subtilis and S.aureus and the abnormal morphologic changes of both bacteria was also found by observation of scanning electron microscope.The result of effect of CE and DCM on respiratory metabolism of bacteria indicated that CE and DCM inhibited bacterial respiration by affecting different respiratory metabolic pathways,namely,CE was involved in regulating both embden meyerhof pathway and tricarboxylic acid cycle pathways of B.subtilis;DCM was involved in regulating the hexose monophosphate of B.subtilis and S. aureus. |
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