Protein profiles in Chlorella spp., Desmodesmus spp., and Scenedesmus spp., grown at temperature range 28°C - 40°C and analysis of DNA fingerprints and β-carotene contents

Abstract

Green microalgae including Chlorella spp., Desmodesmus spp. and Scenedesmus spp. are primary producers in the aquatic ecological systems. Deleterious effects on the primary producers undoubtedly lead to harmful effects on the consumers including human along the food chains. In addition, these microalgae have been found to be microorganisms for the production of useful products at laboratory scale which, with further research, could potentially be scaled-up to pilot and industrial scales. With the imminent global warming and its effects on primary producers including green microalgae and with the industrial importance of selecting fast-growing and heat-tolerant green microalgae for industries, this research was initiated with the aims of selecting fast-growing and heat-tolerant strains from 5 strains each of Chlorella spp., Desmodesmus spp. and Scenedesmus spp. The second aim of the research is to gather preliminary results on mechanisms of heat-tolerance in terms of existing β-carotene contents at 25°C and SDS-PAGE protein profiles when 5.5 x 10[superscript 6] CFU/ml of each strain were grown at 28°C-32°C in a temperature-controlled greenhouse and at 28°C-32°C for 16 h alternated with growth at 40°C for 8 h in a temperature - controlled water bath placed in the greenhouse throughout the experiments. Results of RAPD-PCR fingerprints of the 15 green microalgal strains showed they were different strains. Growth at 25°C showed unicellular green microalgae Chlorella spp. grew more rapidly than multicellular microalgae Desmodesmus spp. and Scenedesmus spp. Growth at 28°C-32°C and at 28°C-32°C for 16 h alternated with 40°C for 8 h showed Chlorella spp. strains PK37 and SS1 were heat-tolerant while Desmodesmus spp. strains NJ40 and SS5 were mesophilic. No correlation was obtained between heat tolerance or mesophilicity properties and contents of β-carotene and polypeptides which had similar molecular weights to those of heat-shock proteins.