Study On Fermentation Characteristics Of Probiotic Lactobacillus Casei Zhang In Solid State System

Probiotic Lactobacillus casei Zhang isolated from Koumiss was used for Solid State Fermentation (SSF). After optimizations of solid media and fermentation conditions, the characteristics of L.casei Zhang in solid state fermentation (water content of media 55%) were compared with the Submerged Fermentation (SMF) (water content of media 90%).The optimal conditions were as follows(g/㎏ medium) :soybean cake 390g, wheat bran 490g, glucose 29g, whey powder 59g, CaCO3 29g, (NH4)2SO4 2g, MgSO4 1g, water content 55%, incubation for 60h. The longer the incubation time, the more the viable count of L.casei Zhang. The viable count of (107.28±17.50)×10~8CFU/g and (24.90±3.68)×10~8CFU/mL were obtained respectively at 60h in SSF and SMF. The utilization of reducing sugar were similar in SSF and SMF. Variations between SSF and SMF in the productivity of exopolysaccharides were significantly different beside 48h(P<0.05).The proteolytic activity of L.casei Zhang increased while the viable count and incubation time increased. And the proteolytic activity was inferior in SSF. The total amount of free amino acid was different between SSF and SMF(P<0.05).The yields of lactic acid and acetic acid changed with time. A lower content of linoleic acid(C18:2) and linolenic acid(C18:3) were detected under SSF conditions than under SMF conditions(P<0.05).The survival rate of L.casei Zhang was 17.51% when the fermentation substrate were dried at 35℃,and the viable count was 39.8×10~8CFU/g.