Production of a diatom-bacteria biofilm in a photobioreactor for aquaculture applications

Navicula veneta biofilm improves the settling of marine larval shellfish. We attempted to optimise the production of N. veneta biofilm by the addition of native bacteria. As a first step, the ability of six bacteria to grow in extracellular products of N. veneta was evaluated, the best growing strain was NC1 (Halomonas sp.). Subsequently, three culture cycles in the Tanaka photobioreactor confirmed that the diatom gave highest production values when cultured with this bacterium, with cell densities of 1.3-2.4 × 10⁶ cells ml^-1; without NC1 the cell production was about 65% less. Comparing microalgal growth, chlorophyll a concentration, and bacterial load showed a positive statistical correlation, verifying that these three variables increased simultaneously. The results suggested the feasibility of using the NC1 strain as a promoter of growth of N. veneta and the potential use of the Tanaka photobioreactor for the mass production of mixed biofilms consisting of diatoms and bacteria, which could be use in settlement of mass cultures of marine invertebrates of commercial importance and/or improving of food in aquaculture.