Biosorption of Cadmium by Thraustochytrids from Philippine Mangroves
Gel Anne Marie V. Atienza1,2*, and Gina R. Dedeles1,2,3
1The Graduate School, University of Santo Tomas, Manila, Philippines
2Pure and Applied Microbiology Laboratory, Research Center for the Natural and Applied Sciences, University of Santo Tomas, Manila, Philippines
3Department of Biological Sciences, College of Science, University of Santo Tomas, Manila, Philippines
Cadmium is a highly toxic element classified as a human carcinogen. As it poses health risks to humans, the utilization of microorganisms capable of biosorbing heavy metals is being explored. Thraustochytrids have occasionally been reported for their tolerance to heavy metals, making them a potential sorbent. This study therefore aimed to isolate thraustochytrids from Philippine mangroves and determine their potential for the biosorption of cadmium. Ten (10) thraustochytrid isolates collected from three mangrove areas were purified and screened for cadmium (Cd) tolerance. After three days of exposure at 6,000ppm, only two isolates, namely ILO7 and BAC9, showed visible growth on agar plates. Meanwhile, ILO7 exhibited slow growth, whereas BAC9 had stable growth in broth cultures. Among the ten isolates, BAC9 was found to be the most tolerant, hence it was used in the succeeding biosorption assays. Morphological and molecular analyses showed that BAC9 was homologous to Aurantiochytrium limacinum ATCC MYA-1381. In the biosorption assay, the total biosorbed Cd using dead cells after 1, 3, and 5h of exposure were 3.8, 4.1, and 8.5%, respectively. Results suggest increased biosorption with increased contact time. For the encapsulated live cells, the total biosorbed Cd was 6.39% in the first cycle and 5.54% in the second cycle, indicating its reusability without efficiency loss. Due to the high tolerance to Cd and biosorption potential of Aurantiochytrium sp. BAC9, it is inferred to be a good candidate for the remediation of Cd or other heavy metals.