Identification, Cultivation And Kinetics Research Of Tetraselmis Sp.-1

Microalgae is the most important primal productivity in the sea, and large-scale cultivation is the most important problem in the exploitation of microalgae. Microalgae can grow in phototrophic, mixotrophic and heterophic cultivations due to its different nutritional styles. In phototrophic cultivation, low cell density, long cultural period, large contamination risk, etc are the big problems. But in mixotrophic or heterophic cultivations, those are not obstacles. Mixotrophic or heterotrophic cultivation of microalgae is the developing tendency of microalgae industry.Tetraselmis sp.-1 is a new microalgae strain constructed by cell fusion technique. In this paper, emphasis was placed upon the construction and identification of Tetraselmis sp.-l, the optimization of the cultural conditions, the influences of light intensity, and the kinetic models of Tetraselmis sp.-l in flask culture and airlift photobioreactor. The results are summarized as follows:1. The protoplasts of rapid-growing microalgae Tetraselmis sp. and phototrophic microalgae Pavlova viridis with high level of EPA and DHA were fused by chemical cell fusion technique, a hybridoma with high level of EPA and DHA and fast growth rate was screened out. The hybridoma was further identified as a new strain by Random Amplified Polymerphic DNA (RAPD) technology and named as Tetraselmis sp.-l.2. In order to optimize the mixotrophic conditions of Tetraselmis sp.-l, we investigated the influences of different conditions on cells density, such as differentlight intensity, inoculation size and different components of cultural medium. The results showed that the suitable light intensity was 2 OOOlx, inoculation size was 10%, glucose and urea were the best carbon and nitrogen resources.3. Response surface methodology (RSM) was used to optimize the medium Tetraselmis sp.-l. Empirical models were developed to describe the relationships between the operating variables (glucose, urea, sodium dehydrogenate phosphate, sodium chloride) and responses (cell density). Statistical analysis indicated that glucose and urea had significant effects on the microalgae cell density, but other two factors (sodium dehydrogenate phosphate, sodium chloride) had no obvious effect. The path of steepest ascent was used to approach the optimal region of the medium composition. Optimal cell density (2.638g dry weight/L) was reached when the operating conditions were glucose concentration (30.75g/L), urea concentration (0.440g/L), sodium dehydrogenate phosphate (15mg/L) and sodium chloride (28g/L).4. The influences of light intensity on specific growth rate, glucose consuming rate, contents of chlorophyll-a and assimilation of NH/ in Tetraselmis sp.-l mixotrophic cultivation were investigated. The results showed that glucose had obviously positive effects on the growth of Tetraselmis sp.-l under same light intensity; and different light intensity had obviously effects on microalgae cell density and glucose consuming rate. The biomass/glucose rate decreased largely with the increasing of light intensity. But contents of chlorophyll-a and assimilation of NH/ were positively influenced by light intensity.5. The growth characteristics of Tetraselmis sp.-l under different cultural conditions were investigated. We set the growth kinetic models of Tetraselmis sp.-l under phototrophic, mixotrophic and heterophic cultivations, the production kinetic models such as chlorophyll-a and total lipid, the substrate (glucose) consumption kinetic model under mixotrophic cultivation. Finally we also calculated the energy yields of Tetraselmis sp.-l under different cultural conditions.Phototrophic growth kinetic model: XP=Xoe~°06+0'203'...