한국 전통 식품인 김치와 젓갈, 탁주로부터 6종의 유산균을 분리하여 동정하였고, 분리된 유산균의 생육에 대한 chitosan 및 분자량별로 분리된 그것의 COSs의 효능을 검증하기 위해 유산균 배양액의 pH 변화 및 유기산 분석과 유산균의 성장을 확인하였다. 본 연구결과에서는 chitosan과 고분자량의 COS3가 분리된 대부분의 유산균에 대한 현저한 성장 저해 효과를 보였으나, 분자량이 낮은 COS1과 COS2는 모든 유산균의 성장을 저해시키지 않았고, 현저하게 촉진시킴으로서 유기산의 생성을 유도하여 pH를 저하시켰다는 것을 확인했다. 이 모든 결과를 미루어볼 때, 본 연구는 유산균의 성장을 저해하는 chitosan을 저분자화 시켜 제조한 COS1과 COS2가 장내 유용 세균으로 알려진 유산균의 성장을 촉진시켜 어류 양식 산업에 있어 유산균제제와 함께 첨가 시 장내 면역을 증강시키는 유용한 사료첨가제로서 사용될 수 있을 것으로 사료되며, 더 나아가 인간 장내의 대량으로 존재하는 유용균에 대한 prebiotics로서 작용될 수 있음을 제시한다.

Chitosan and its oligosaccharides have shown antimicrobial effects against pathogenic bacteria inducing fish diseases. Lactic acid bacterium (LABs) known as probiotics play important roles in the regulation or maintenance of normal flora and pathogenic bacteria. In this study, we elucidated the potential of chitosan and its oligosaccharides as natural prebiotics inducing the growth of lactic acid bacterium (LABs). First of all, we prepared three chitosan oligosaccharides (COSs, COS1; molecular weight (MW)1 KDa>, COS2; MW 1~5 KDa, COS3; MW 5~10 KDa) by enzymatic hydrolysis of chitosan and isolated the 6 kinds of proteolytic LABs (BK1, BK2, BK14, BK18, BK19, and BK20) from Korean traditional foods such as Kimchi, fish fermented foods and rice wine. Among the chitosan and its three MW fractions, the two low MW fractions, COS1 and COS2 markedly decreased pH by increasing the production of organic acids, especially lactic acid and formic acid in the all LABs-cultured mediums. In contrast, the high MW fraction, COS3 significantly decreased pH with the increment of the lactic acid produced in the only BK19-cultured medium and did not affect to the others. Also, COS1 and COS2 significantly induced the growth ofLABs at all the concentrations, whereas COS3 and chitosan inhibited them. In particular, COS1 showed the highest growth effects for the 6 kinds of LABs from fish fermented foods (Jeotgal), compared to those of two other fractions and chitosan. Itwas better than them of LABs isolated from Kimchi (BK1 and BK2). Taken together, the low MW fractions of chitosan led to the growth of six LABs with the change of pH and the production of organic acids. This study suggests that the low MW fractions of COSs can be used as useful prebiotics to improve fish diseases as the animal feeds.