蒟蒻及其水解產物對乳酸菌醱酵產物之影響

人類腸道內所分佈之菌相，至今已被分離鑑定出約有400種以上之菌種存在，其中Bifidobacterium及Lactobacillus對健康之正面影響遠超過負面影響。 蒟蒻精粉（Konjac powder）富含葡萄糖及甘露糖β鍵結而成之水溶性纖維，所以不為人體消化吸收，本實驗即以體外試驗觀察腸內菌對蒟蒻及其不同分子量水解產物之利用性。利用酸解法將蒟蒻精粉（K）製備成三個不同分子量之水解產物，所得之平均聚合度（Degree of polymerization, DP）各為26（KH1）、12（KH2）及5（KH3）。將蒟蒻和這三個水解產物（0.05﹪, w/v）添加至培養基中，觀察這些碳源對B. adolescentis、B. bifidum、B. breve、B. longum、L. acidophilus、Bacteroides fragilis等六株腸內菌之生長情形，並比較此六株腸內菌於各碳源中其醱酵產物之影響。 結果發現，在添加0.05﹪之各碳源於培養基中，六株腸內菌之生長曲線皆會隨著培養時間之增長而上升，並能利用這些碳源醱酵產生短鏈脂肪酸及乳酸，使培養液之pH值下降。就短鏈脂肪而言，比較添加K、KH1、KH2及KH3之培養基，發現對Konjac有良好之醱酵者為B. adolescentis和L. acidophilus二株菌；對KH1者為B. bifidum及B. breve；KH3則是Bacteroides fraigilis。在乳酸方面，以B. breve和B. longum二株菌對於添加KH2之培養液所產生之乳酸量最多，其他菌株於各碳源下則無顯著性差異。 分析其醱酵產物之抗氧化性中，結果顯示六株腸內菌皆以添加KH1培養基中具較佳之螯合鐵能力；以添加KH3中具較佳之共軛雙烯清除率；而清除DPPH自由基方面，於添加KH3之培養基中有較佳之DPPH自由基清除率者為B. adolescentis、 B. bifidum、L. acidophilus三株菌， KH2中為B. breve， KH1為B. longum， Konjac中則為Bacteroides fraigilis；在其氧化產物方面，B. bifidum及L. acidophilus於Konjac中有較高濃度之氧化產物，Bacteroides fragilis於KH1中，B. adolescentis、B. longum二株菌則於KH2中所測得之濃度較高，其中B. breve雖然於各碳源間無顯著差異性，但其脂質過氧化產物之濃度為六株菌之冠。由以上結果得知，蒟蒻及其水解產物對腸內細菌具良好之利用性，且依菌株之不同，對利用各碳源之情形亦不同。

The aims of this study were to investigate the prebiotic role of konjac glucomannan and its hydrolysates, and the antioxidative effects of the fermentation products from six species of the intestinal microorganism including Bifidobacterium adolescentis, B. bifidum, B. breve, B. longum, Lactobacillus acidophilus and Bacteroides fragilis. The acid hydrolysates of konjac were fractionated into three portions according to their degree of polymerization (DP) into KH1 (mean DP=26), KH2 (mean DP=12) and KH3 (mean DP=5). Culture media containing 0.05% konjac, its hydrolysates, simple sugars and fructo-oligosaccharide were inoculated with respective microorganism. The optical absorbance and culture pH were monitored after 6, 12, 24 and 48 h of incubation. The lactate and short chain fatty acid content, antioxidative ability and peroxidative products were determined after 48 h of incubation. The results indicated the optical absorbance and the decrease in culture pH were increased with the duration of incubation. Konjac itself was better substrates for fermentation for Bifidobacterium adoelscentis and L. acidophilus, but not for other Bifidobacterium spp. and Bacteroides fragilis. However, when compared with konjac hydrolysates, KH1 and KH3 were better utilized by B. bifidum and B. breve, respectively, than the other bacteria. The media containing KH3, as compared with konjac and other konjac hydrolysates, produced the greatest amount of short chain fatty acids by Bacteroides fragilis. In terms of lactate production, KH2 was the best substrate for B. breve and B. longum. The lactate production did not vary with carbohydrate substrates in other species. In terms of antioxidative capacity, KH1-containing media compared with other carbohydrate sources exerted the greatest ability in all species. On the other hand, KH3-containing media compared with other carbohydrate sources exerted the greatest diene clearing ability in all species. KH3-containing media resulted in best DPPH clearing ability in B. adolescentis, B. bifidum, and Lactobacillus acidophilus. KH2, KH1, and konjac caused the greatest DPPH clearing ability in B. breve, B. longum and Bacteroides fragilis, respectively. Furthermore, konjac caused greater oxidative products in B. bifidum and L. acidophilus. KH1 caused the greater peroxidative product contents in Bacteroides fragilis. B. adolescentis and B. longum produced greatest peroxidative products in KH2-containing media. In particular, B. breve produced the greatest amount of peroxidative products as compared to other species, and the production was not affected by carbohydrate sources. In summary, the konjac and its hydrolysate could specifically stimulate the growth of lactic acid bacteria or the production of organic acids. However, the preference of carbohydrate varied with species. Similarly, the antioxidative effects of fermentation products varied with carbohydrate sources, and the microbial species. The healthy aspects of prebiotic/ probiotic system deserve further investigation.