菌株Aeromonas veronii DYU-Too 19分解幾丁質生合成還原醣之最適碳源與氮源濃度探討

Optimal Concentrations of Carbon and Nitrogen in Aeromonas veronii DYU-Too 19 for the Production of Reducing Sugars through Chitin Degradation

本研究從彰化縣大村鄉田間土壤取樣，篩選出具幾丁質分解酵素之菌株Aeromonas veronii DYU-Too 19，探討菌株分解幾丁質之最適培養條件。以”一次一因子”法先探討不同碳源種類和濃度及氮源蛋白腖（peptone）濃度對菌株Aeromonas veronii DYU-Too 19之幾丁質分解酶活性和還原醣生成量之影響，再以反應曲面法探討菌株分解幾丁質生合成還原醣之最適培養條件。結果顯示，5％ β-幾丁質培養之幾丁質分解酶活性最高為1,572 U／L。4％ β-幾丁質培養，具最高還原醣產量15.4g／L；以蛋白腖為氮源時，濃度為0.5 g／L之培養，幾丁質分解酶活性最高為1,850U／L，還原醣產量為12.5g／L。進行中心混成試驗，探討菌株Aeromonas veronii DYU-Too 19生成還原醣之最適化培養條件。結果顯示，β-幾丁質含量與蛋白腖含量兩因子，對還原醣生成量達到顯著水準（p＜0.05），由反應曲面法獲得碳氮源最適培養組成為4.42％ β-幾丁質與0.55 g／L蛋白腖，預估最大還原醣產量20.52 g／L。經由發酵培養驗證最適化條件，還原醣產量為20.24 g／L，實驗值與預測值並無太大差異，表示此一回應模式能適切預測菌株Aeromonas veronii DYU-Too 19生產還原醣之產量。 In this study, Aeromonas veronii DYU-Too 19 obtained in Dacun, Changhua, Taiwan was screened for chitin degradation. This study explored the optimal cultivation conditions of Aeromonas veronii DYU-Too 19 for the breakdown of chitin. The one-factor-at-a-time method was used to investigate the effect of different carbon sources and concentrations as well as peptone concentrations on chitinase activity and the production of reducing sugar. Response surface methodology was used to explore optimal cultivation conditions for the production of reducing sugars through chitin degradation. The results showed that the highest chitinase activity in 5% β-chitin culture was 1,572 U/L. The highest proportion of reducing sugar was 15.4 g/L in 4% β-chitin culture. When 0.5 g/L peptone was the nitrogen source, the highest chitinase activity and reducing-sugar proportion were 1,850 U/L and 12.5 g/L, respectively. Central composite design was used to investigate the optimal cultivation conditions for the production of reducing sugars by Aeromonas veronii DYU-Too 19. The concentrations of β-chitin and peptone were significantly related to the level of reducing-sugar production (p < 0.05). The optimal cultivation condition obtained by the response surface methodology was 4.42% β-chitin and 0.55 g/L peptone, which had the maximum reducing-sugar yield 20.52 g/L. The optimal cultivation conditions yielded 20.24 g/L reducing sugar. No significant difference was observed between the experimental and the predicted values. Therefore, this response model can accurately predict the yield of reducing sugar produced by Aeromonas veronii DYU-Too 19.