The Scale-up And Optimization For Acarbose Fermentation By Actinoplanes Sp. A-5.6

Acarbose, a pseudo-oligosaccharide, is produced by Actinoplanes sp, which acts as a competitive a-glucosidase inhibitor. Due to be hardly digestible and generally have no detectable toxicity, acarbose has widely been used in the therapy of diabetes type II (non-insulin-dependent), which could better control blood sugar contents of patients after meals. In this paper, according to the key factors effected the cell growth and acarbose biosynthesis in Actinoplanes sp. A-5.6, a series of fermentation control strategies were implemented in shake-flask,100L and30-m3fermenter. As a result, a scale-up strategy was successfully established for industrial acarbose fermentation.The seed medium and fermentation were firstly optimized. As a result, the optimal seed medium for Actinoplanes sp. A-5.6was composed of (g/L):glucose,30; soy bean flour,40; KH2PO4,1.0; MgSO4,1.0. The demand characteristics of carbon sources and nitrogen sources of Actinoplanes sp. A-5.6were then investigated. Based on this fact, the concentrations of the fermentation components were further optimized with central composite design and response surface analysis. As a result, the final composition of the optimal medium for Actinoplanes sp. A-5.6fermentation was as follow (g/L):glucose,30; maltose,61.25; corn steep liquor,17.50; soybean flour,20; monosodium glutamate,1.0; CaCl2,2.0; FeCl3,0.5; K2HPO41.0; CaCO32.5. By using this optimization strategy, the acarbose yield obtained under the optimal medium was increased from837mg/L to1043mg/L, with24.61%higher than that obtained with the original medium recipe.Secondly, the fermentation control strategies in shake-flask and100L fermenter were performed. The results in shake-flask fermentation revealed that48h of seed age,180-200rpm of revolution,30mL of a medium volume in250mL shake-flask,7.0of an initial medium pH and10%of an inoculum volume were the optimal fermentation conditions for Actinoplanes sp. A-5.6. The results obtained in shake-flask cultivation demonstrated that the ratio of maltose and glucose had significant effect on acarbose biosynthesis, and the feeding medium containing3:1(mass ratio) of maltose and glucose was favorable for acarbose production. Then the correlation of carbon source concentration with acarbose production was further investigated in100L fermenter, and the results showed that7.5-8.0g/100ml of total sugar and4.0-4.5g/100ml of reducing sugar were optimal for acarbose production. The pH and DO control strategies were investigated for the fermentation of acarbose in100L fermenter, and the results showed that the optimum pH and DO were7.00-7.20and30%, respectively. In the case of this fermentation conditions, acarbose production was stably kept at4000-4100mg/L.Finally, the scale-up strategy and optimization for acarbose fermentation by Actinoplanes sp. A-5.6were explored. Based on the results in100L fermenter, an effective and simplified scale-up strategy was successfully established for acarbose fermentation in a30-m3fermenter, by using total sugar and reducing sugar as the scale-up parameter. Under this scale-up strategy, the total sugar and reducing sugar were maintained at7.5-8.0g/100ml and4.5-5.0g/100ml during the fermentation process in30-m3fermenter. As a result,4327mg/L of acarbose was obtained at168h of fermentation. Simultaneously, the seed age, pH and DO were further investigated, and the results showed that the telophase seed,7.00-7.20of pH and30%DO were favorable for acarbose fermention. In the case of the optimal fermentation conditions, a4400mg/L of acarbose was obtained in30-m3fermenter.