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Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00404

    Bacillus subtilis D9 may purify coastal aquaculture wastewater and improve grass carp Ctenopharyngodon idellus resistance to disease caused by Vibrio parahaemolyticus

    Yalu Shao, Hua Zhong*, Liangkai Wang, Mohammed M. A. Elbashier

    *Corresponding author:

    ABSTRACT: In the coastal areas of China, high-density aquaculture has caused environmental problems and fish health concerns. Bacillus subtilis D9 is a new strain isolated from the coastal soils which could be used in the coastal aquaculture industry as a promising microbial agent. The objective of this study was to investigate the effect of B. subtilis D9 on the purification of coastal aquaculture wastewater and the disease resistance of grass carp Ctenopharyngodon Idellus. In this study, 3 inoculation levels of B. subtilis D9 including 5.5 ×1 07 cfu ml–1 (BD7), 5.5×108 cfu ml–1 (BD8) and 5.5×109 cfu ml–1 (BD9) were used, together with sterilized saline water (Control, without B. subtilis D9). B. subtilis D9 at BD8 reached the maximum removal rates of 81, 87, 91, 52 and 86% for NH4+-N, NO3--N, TN, NO2--N and turbidity, respectively, after 25 d of treatment. This was significantly higher (p < 0.05) than at BD7, BD9 and Control. Furthermore, BD8 under the aeration condition (AIR) showed removal rates of 93, 91, 95, 76 and 89% for NH4+-N, NO3--N, TN, NO2--N and turbidity, respectively. In contrast, these values were only 26, 29, 16, 10 and 57% for BD8 under inactivated bacteria liquid (IBL). Significant differences (p < 0.05) were found in weight gain, specific growth rate and the relative percentage of survival of grass carp among AIR, BD8, and IBL groups after 22 d of infection by Vibrio parahaemolyticus. It may be concluded that B. subtilis D9 with an aeration condition had beneficial effects on the purification of the coastal aquaculture wastewater and the disease resistance of grass carp to V. parahaemolyticus.