The influence of wastewater pretreatment, attachment material, and inoculation strategy on the growth of target algal species in cultivated biofilms

Microalgal biofilms are promising sources of sustainable biofuels and bioproducts because of their minimal growth requirements, ability to sequester CO 2 , and high biomass concentrations. However, strategies to enhance the growth of product-producing species within the biofilm communities must be investigated to optimize the performance and profitability of algal biofilm cultivation systems. Quantitative polymerase chain reaction assays were used to investigate how wastewater, biofilm attachment material, and inoculation strategies influence the abundance of Chlorella vulgaris and Scenedesmus obliquus in biofilms. A 5.6-fold increase in biofilm dry weight was achieved by pretreating reactors with wastewater and using cotton biofilm attachment materials compared to that on non-pretreated polycarbonate attachment materials. Furthermore, depending on the inoculation strategy and the presence of wastewater, the composition of the algal community in biofilms differed from their corresponding suspensions and from the inoculums, highlighting the importance of analyzing the species in algal biofilms in cultivation systems. This study represents the first application of quantitative polymerase chain reaction to estimate cell abundance of C. vulgaris and S. obliquus in cultivated algal biofilms and provides insights into the optimization of algal biofilm cultivation systems for the commercialization of algal biofuels or other bioproducts.