Screening For Alginate Degrading Bacteria And Application In Aquaculture Of Sea Cucumber(Apostichopus Japonicus)

In recent years, with the rapid development of sea cucumber aquaculture, artificial feed industry has been gradually developed as its main sub-industry. However, many shortcomings of artificial feed such as incomprehensive nutrition, uneasy digestion and doping variety of pathogenic bacteria resulted in slow growth of sea cucumber and utilization rate of feed. These threatend the sea cucumber health in a lot of feed-waste and farming cost. Fermented feed has many advantages, such as better palatability, growth and immunity improvement of animals, but researches on sea cucumber fermented feed are rare. Therefore, developing a safe and nutritious fermented feed become the focus for the development of sea cucumber feed industry.A strain of bacteria which can degrade alginic acid had been screened, it was mixed with EM bacteria(lactic acid bacteria, yeast and bacillus subtilis) to prepare the EM-alginic acid bacteria product and applied it to solid-state fermentation of sea cucumber feed. We investigated the differents between fermentated feed and unfermented feed on qualities, and effects of different feeds on growth performance, digestion, immunity and body composition of javeniles Apostichopus japonicus. The results of sensory, physical and chemical experiments showed that fermented feed had a better palatability and attractant to sea cucumber, a higer ratios of crude protein, free amino acids and reducing sugars and a lower ratios of crude fiber, crude ash and alginic acid were found in the unfermented feed.Feeding trials were composed of three treatment groups: the control group(unfermented feed), group A1(feed fermented with alginic acid decomposing bacteria and EM becteria) and group A2(feed fermented with EM becteria), respectively. The breeding experiments of 60 days were done with the juvenile Apostichopus japonicus of 6.25 g initial body weight. The results showed that, the fermented feed of group A1 could significantly improve Apostichopus japonicus survival rate(95.33%), final weight(10.11 g/individual) and protein apparent digestibility(86.47%). At the same time, fermented feed of group A1 could significantly increased the contents of body wall crude protein, crude fat, and 18 kinds of amino acid compared with the control, and better than the fermented feed of group A2. Digestive enzyme assays showed that fermented feed of A1 could significantly improve activities of amylase(233.18 U/mg prot), cellulase(326.64 U/mg prot), alginic acid enzyme(439.55 U/mg prot) and protease(681.15 U/mg prot), which implied that fermented feed could significantly improve Apostichopus japonicus digestibility of diet, and better than group A2. The results of Apostichopus japonicus coelomic fluid non-specific immune-related indicators(ACP, AKP, SOD, T-NOS, CAT and LSZ) showed that feed of group A1 could significantly improve the activities of AKP and SOD, while EM feed(group A2) had no significantly effects on these six kinds of enzyme activities. Further more, fermented feed of group A1 had better applicative effects on Apostichopus japonicus aquaculture. In summary, alginic acid degrading bacteria played an important role in feed fermentation and fermented feed could significantly improve the growth performance, digestion and non-specific immunity of Apostichopus japonicus, which had a market prospects.