Research On Mycelial Morphology And Continuous Fermentation Of Rhizopus Oryzae Immobilized By Corn Cob In L-lactic Acid Production

L-lactic acid is a very versatile organic acid,and corn cob is abundant organic waste in agriculture.In this paper,rhizopus oryzae immobilized with agricultural waste corn cob fermentative production L-lactic acid,studied the relationship between rheological properties and produce acid in fermented liquid,and morphological features were described in the fermentation process of mycelium pellet and corn cob,finally the preliminary explored the PFR reactor for L-lactic acid continuous fermentation,the main contents and results are as follows.Laboratory screening of rhizopus oryzae R-6-1 as starting strain,under different corn cobs and glucose addition proportion to research the fermented liquid rheological properties,the best addition proportion of corn cobs and glucose is 1:4,The corn cob can be a very good adsorptive immobilized rhizopus oryzae R-6-1 form the mycelium pellet to produce acid at this time,can make the fermented liquid is clear,viscosity is low between 1 to 2 m Pa·s,rheological properties of flask fermented liquid to improved,nutrients and oxygen transfer effect is good,L-lactic acid accumulation of up to 30 g/L,sugar acid conversion rate 79.96%,12%more than pure sugar fermentation,L-lactic acid accumulation were promoted.contrastive research between the fermented liquid viscosity changes of fermentation tank and shaking flask,the fermented liquid viscosity change trend are the same,the fermentation tank fermented liquid viscosity is significantly higher than shaking flask fermented liquid viscosity,however,the acid yield efficiency of fermentation tank higher than shake flask fermentation.Through the fermentation process mycelium morphology change with fermentation time were measured,in the fermentation process mycelium pellet to quantify the morphological description.In 0-12 h spore will swell,12 to 20 h spore germination form mycelium;In 20 to28 h mycelium closer winding corn cob;28h to fermentation anaphase can form mycelium mass and mycelium pellet.After fermentation tank 48 h,cascade control parameter,mycelium form mycelium pellet of average diameter(short axis)4 mm,the determination of microscopic imaging system,average the short axis is 4.7 mm and long axis is 4 mm,the mycelium pellet cross-sectional area of 20 mm~2 is good for produce acid.Produce acid amount of 34.9 g/L,the percent conversion of 72.25%.Corn cob 8 h samples when seen from the SEM,fermentation and not fermentation form not difference the size of corn cob,When20 h,the samples of a more obvious osteoporosis holes;32 h holes become far larger and more,after 10?20 microns in diameter,very suitable for mycelium.From the corn cob microstructure explained the mechanism of mycelium pellet into a ball.Use PFR reactor to continuous fermentation,the fermentation process can be divided into three stages it is mycelia recovery,high efficient produce acid and mycelia recession;Fermentation column specifications respectively choose long tube(inner diameter 26 mm,length 80 cm)and short tube(inner diameter 16 mm,length 30 cm),long tube fermentation column L-lactic acid production and sugar consumption were significantly higher than short tube column fermentation,sugar to acid percent conversion of long tube fermentation column were significantly higher than the short tube,reached 72%and increase 18%,fermentation efficiency is superior to the short tube fermentation column.In addition,the fermentation period of 24 h compared with fermentation period of 12 h,found that the former sugar consumption is significantly higher than the latter and increase 15%.L-lactic acid production and sugar to acid percent conversion were significantly higher than the latter.The contrast of mycelium morphology,found the process that before and after continuous fermentation mycelium pellet from strong biological activity to recession.