Laboratory algal assay of induced competition to study the role of contamination on oil production in mass cultures

Since the interspecific competition represents a critical issue for biodiesel production in open mass cultures, a laboratory approach based on the method of multisizing cell counting was developed to monitor the competition course of single algal species grown in mixed cultures. Two freshwater microalgae, Pseudokirchneriella subcapitata and Scenedesmus quadricauda, were used to set-up an induced-contamination assay, with the aim to test their competitive capabilities and to investigate the effect of competition on oil yield. The multisizer-counting method revealed effective to selectively measure the algal growth of single species in mixed cultures, supporting the advantages of Pseudokirchneriella as competitive abilities and as overall productivity even in mixed-culture conditions. Particularly the high oil production, which was not markedly lowered by the contamination event, is supporting the suitability of Pseudokirchneriella to be used in open mass cultures. In general, the adopted approach supports the potential of laboratory algal assays for preliminary screening to drive species selection, based on their competitiveness, to prevent the risk of lowering the oil yield in outdoor systems for biodiesel production.