Chitosan-harvested polyhydroxybutyrate-rich Zobellella denitrificans ZD1 as a multifunction feed for aquaculture

Abstract

The security of the aquaculture industry is jeopardized by antibiotics overuse and increasing demand for aquaculture feeds, which remain heavily derived from capture fisheries. Biopolymer poly(3-hydroxybutyrate) (PHB) and some microorganisms are promising replacements for antibiotics and aquaculture feed, respectively. Therefore, we investigated the potential of using chitosan-harvested PHB-rich Zobellella denitrificans ZD1 (designated as CP-ZD1 hereafter) as a multifunction feed for brine shrimp Artemia (model species). Both PHB and chitosan and their intermediates (3-hydroxybutyrate and chitosan oligosaccharides) showed antimicrobial properties toward three known aquaculture pathogens (Vibrio campbellii, Aeromonas hydrophila, and Streptococcus agalactiae) and non-pathogens (non-pathogenic Escherichia coli, Bacillus megaterium, and Rhodococcus jostii RHA1). Low doses of 3-hydroxybutyrate and chitosan oligosaccharides mixtures effectively suppressed the growth of the pathogens. When supplied with CP-ZD1, the starved Artemia showed prolonged survival and a healthy gut microbiome, suggesting that CP-ZD1 can serve as a feed/energy source. Up to 80% enhanced survival and immune response was observed in pathogenic V. campbellii-challenged Artemia when fed with CP-ZD1. Overall, the results showed that CP-ZD1 could serve as an efficient biocontrol agent, a feed/energy source, and an immunostimulant in support of sustainable aquaculture.