Fatty Acids Released by Chlorella vulgaris and Their Role in Interference with Pseudokirchneriella subcapitata: Experiments and Modelling

Abstract

The role of extracellular fatty acids in the interference between two algae, Chlorella vulgaris Beijerink and Pseudokirchneriella subcapitata (Korshikov) Hindak, was assessed by the co-cultivation of the two selected strains, as well as by the chemical analysis of exudates from the culture media of single strain cultures. The effect of culture age and phosphate limitation was evaluated. The experiments showed that the composition and amount of fatty acids, released by C. vulgaris and by P. subcapitata, both in a batch and in a continuous monoculture, depend on the culture age and on the phosphate concentration in the culture medium. We also found that the amount of chlorellin generated in the two algae co-culture increased and was almost exclusively constituted by a mixture of C18 fatty acids. By using the evaluated concentrations of these fatty acids, an artificial chlorellin was prepared. The toxicity of this mixture to P. subcapitata appears to be similar to that of the natural chlorellin. For both algae, a stimulation of growth was observed at low concentrations of the natural chlorellin, whereas higher concentrations produced inhibitory effects on both species. However, P. subcapitata was much more sensitive than C. vulgaris. By using some of these new experimental results, two new mathematical models have been used to describe the toxicity of chlorellin to C. vulgaris and to the interference between C. vulgaris and P. subcapitata, respectively.

Cultivation of Algae in Vegetable and Fruit Canning Industrial Wastewater Treatment Effluent for Tilapia (Oreochromis niloticus) Feed Supplement

“…Moreover, it has been found that chlorellin at lower concentration still allows algae to grow. However, if chlorellin is present at a concentration greater than 6.5 mg/L, it affects growth (DellaGreca et al, 2010). Chlorellin extracted from aged Chlorella sp.…”

Scavenging Effect of Various Extracts of the Gymnema sylvestre R. Br. and Antioxidant Activity of the Isolated Triterpenes

“…Rat diploid immortalised fibroblasts represent one of the simplest available and widely used cellular models for toxicological assays because rat and human cells exhibit good metabolic similarity, and the results obtained with rat cells are typically confirmed in humans. Cytotoxicity assays were performed using the MTT test, as previously described [16,23,[26][27][28][29][30].…”

Impairment of benthic diatom adhesion and photosynthetic activity by allelopathic compounds from a green alga: involvement of free fatty acids?

“…One of the first algal allelopathic compounds described in literature, "chlorellin," from Chlorella vulgaris (Pratt et al 1944), is a mixture of C18 fatty acids (DellaGreca et al 2010;Scutt 1964). PUFAs, and especially C18 like LA, LNA, and oleic acid, exhibited toxicity against various green algae and cyanobacteria (see reviews by Ikawa 2004;Watson 2003).…”

“…Moreover, among the allelopathic compounds described in literature, many are produced by benthic microorganisms, like nostocine A from the cyanobacteria Nostoc spongiaeforme (Hirata et al 2003) or fischerellin A from the cyanobacteria Fischerella muscicola (Hagmann and Jüttner 1996). The chemical nature of allelopathic compounds is very diverse; they can be phenolic compounds (Pouvreau et al 2007), fatty acids (DellaGreca et al 2010), or halocarbons (Vanelslander et al 2012) for instance.…”