Co-cultivation and stepwise cultivation of Chaetoceros muelleri and Amphora sp. for fucoxanthin production under gradual salinity increase

Abstract

In a seawater-based open pond microalgae cultivation system salinity will increase gradually over time due to evaporative loss. Continuous salinity increase would lead to non-optimal salinities which negatively affect the biomass and fucoxanthin productivity. To increase and maintain high overall biomass and fucoxanthin productivity, even in the non-optimal salinity zone, two cultivation methods for marine and halotolerant microalgae were carried out, co-cultivation and stepwise cultivation (sequential cultivation). Two fucoxanthin-producing diatoms, Chaetoceros muelleri (marine) and Amphora sp. (halotolerant), were cultivated at non-optimal salinities between 59 and 65‰. Stepwise cultivation showed approximately 63% higher total biomass and 47% higher fucoxanthin productivity than that of co-culture. The ability to reutilize culture media in the stepwise cultivation increases the sustainability of that method. The use of a stepwise culture regime, coupled with a regimen of gradually increasing salinity, provides the possibility of year round fucoxanthin production from microalgae.