NOVELTY - Improving sisal hemp saponin yield using microbial fermentation comprises chopping potatoes, adding water, boiling, filtering, taking filtrate in a conical flask, adding agar, sterilizing and pouring into a culture dish to obtain a solid culture medium, sterilizing the remaining filtrate to obtain a liquid fermentation culture medium, inoculating the target strain on the solid culture medium, incubating and inoculating into liquid fermentation culture medium and fermenting, centrifuging, adding sterile water into pellet, adding sisal waste, fermenting, centrifuging and drying the supernatant.    USE - The method is useful for improving sisal hemp saponin yield using microbial fermentation (claimed).    ADVANTAGE - The method increases 30% more productivity compared to an acid-base chemical extraction method. The microorganism is safe, environmental-friendly and economical; has rapid degradation velocity with high degradation rate.    DETAILED DESCRIPTION - Improving sisal hemp saponin yield using microbial fermentation comprises: (i) preparing culture medium including: (i.a) peeling 100-250 g potatoes, chopping, adding 0.5-2 l water into it and boiling for 20-40 minutes, cooling to room temperature and filtering via a four layered gauge to obtain 0.5-2 l filtrate; (i.b) taking 0.05-1.5 l filtrate in a conical flask, adding 1-2 g agar into it, wrapping the conical flask mouth with brown paper and sterilizing at 121 degrees C with a pressure of 1.103 MPa for 20 minutes, pouring the product from the conical flask into a culture dish having 9 cm inner diameter and allowing the agar to solidify to obtain a solid culture medium; and (i.c) transferring the remaining 0.5-1.95 l filtrate into 1-2.5 l container, wrapping the conical flask mouth with brown paper and sterilizing at 121 degrees C with a pressure of 1.103 MPa for 20 minutes to obtain a liquid fermentation culture medium; (ii) culturing and fermenting the target strain by inoculating the preserved target strain slant on the obtained solid culture medium under aseptic condition, incubating at 20-35 degrees C for 36 hours, then taking out the strain and inoculating into 50-200 ml obtained liquid fermentation culture medium and fermenting at 28-36 degrees C for 72 hours on a rotating shaker at a speed of 100-300 rotations/minute to obtain fermentation broth, where the target microbial strain is Corynebacterium species GLHZB21 (CCTCC NO: M2011050, February 25th, 2011); and (iii) extracting sisal hemp saponin from sisal hemp waste material including taking 30 ml fermentation broth in a centrifuge tube, centrifuging at 4000-6000 rotations/minute for 20 minutes, discarding the supernatant, adding 100 ml sterile water into pellet and diluting, adding 5-20 g sisal waste material, fermenting on a shaker at 200 rotations/minute for 24 hours, taking 5 ml fermentation broth and centrifuging at 4000- 6000 rotations/minute for 15 minutes and drying the supernatant in a vacuum oven to obtain the sisal saponin extract.