Medium optimisation as a first step towards the feasible production of biopolymers with Botryococcus braunii

Abstract

Current interest in the production of commercial biopolymers which are derived from renewable resources arises from the necessity to move from a fossil-based to a more sustainable economy. Microalgae are considered potential biopolymer producers although their use at an industrial scale is not feasible yet. In this sense, medium optimisation and operational conditions can be considered the first steps leading to growth and product productivity enhancement which are a prerequisite to boost the microalgae industry. This manuscript describes medium optimisation for two promising strains of the green alga Botryococcus braunii, B. braunii CCALA-778 (race A) and B. braunii AC761 (race B), which are natural producers of (exo)polysaccharides and hydrocarbons of high interest in the biopolymers industry. Medium optimisation was based on a three-step research process: (i) a literature survey to identify macro- and micronutrients that could be limiting Botryococcus growth, (ii) a 3-level factorial design experiment in microwell plates to evaluate modified media accordingly and (iii) validation of previous results in batch cultivation in Roux flasks. The results obtained show the significant impact of culture media optimisation in the growth dynamics and valuable compound accumulation of B. braunii. Attention should be given to each particular Botryococcus race and media should be defined accordingly. But overall, the new optimised media resulted in higher productivities which may contribute to reach sustainability of Botryococcus cultivation.