Abstract
Chlorella Pyrenoidosa was rich in various nutrients, so it has been marketed as health food for a period of time. Our result indicated that Chlorella Pyrenoidosa, isolated locally and morphologically identified by local authority, may manifest the toxicity of toxic contaminant by increasing its quantity, which may impose a potential food safety concern. In the 1-h incubation studies, Chlorella Pyrenoidosa was found to exhibit differential stress response to different environmental toxic contaminants. The dead algal cells were shown to bind organic toxic chemicals in the decreasing order of 2,4,6Trichlorophenol (TCP), -Toluidine (TD), O-cresol (OC), 4Bromoaniline (4BA), 4-Nitrophenol (4NP) and 4-Nitroaniline (4NA). The live algal cells exhibited additional handling of organic compounds in the form of internalization, desorption and secretion. Based on the HPLC analysis, algae was found to secrete the toxic organic chemical 4NA that originally exposed to it, to the medium with the amount exceeded the original added quantity. The manner of net secretion was concentration dependent. Higher the exposure concentration induced more chemical to be secreted. Spectrum analysis using multiple wavelengths did not reveal significant change in the spectrum absorption of test chemicals. The observed phenomena might indicate that the local algae were triggered by the exposure of 4NA to re/produce the same compound and net secrete out from the cell, and potentially manifested the toxicity of 4NA. The net secretion process was found not to be oxygen dependent. It was hypothesized the secretion may be a stress shock event leading to a condition of cell leakage. Further studies were required to elucidate the mechanism. The internalization of TCP, TD and 4BA by live algal cell were observed and the process was inhibited in the absence of oxygen. For 4NP, desorption was observed in live algal cells .
Highlights
Algae were known to be inducible by environmental stress to produce secondary metabolites (Chen et al 2009, Peckol et al 1996, Sotka et al 2002)
When TCP was incubated with dead algal cells, it would bind onto the cells, (Fig. 1b) and decrease the TCP concentration in the supernatant
There were at least four handling processes observed in local Chlorella Pyrenoidosa to environmental contaminants
Summary
Algae were known to be inducible by environmental stress to produce secondary metabolites (Chen et al 2009, Peckol et al 1996, Sotka et al 2002). Producing secondary metabolite by algae was a kind of defense mechanism to increase their chances of survival or decrease pathogenic attack. Some algal species might produce secondary metabolites under nutrient limitation or altered nutrient (N,P) ratios, which would inhibit potential competitors and so increased their competitiveness in grasping resources (Graneli et al 2008). Accumulation of unpalatable secondary metabolites (Amsler & Fairhead 2006) was one of the strategies to increase their survival by reducing the chance of being grazed upon (Pansch et al 2008, Sotka et al 2002).
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