Molecular characterization of local microalgae and evaluation of their potential use for biodiesel production and as plant disease control agents -

Abstract

Microalgae are prokaryotic or eukaryotic photosynthetic microorganisms that have received a lot of attention in the past decade. Other than microscopy and cytology, no efforts have been conducted for identifying local microalgae using molecular techniques. In this study 12 local isolates were isolated and successfully grown in culture media and of which six were identified to the genus level and three to the species level using barcode markers. An additional three isolates obtained from Greece and Egypt were also identified. The isolates were identified as Chlorella sp., Chloroccum sp., Dunaliella sp., Melosira dubia, Fistulifera sp.,Nannochloropsis sp., Chlamydomonas sp., and three different Tetraselmis species. In recent decades, the ability of microalgae to accumulate high levels of lipids under certain culture conditions motivated researchers to explore the possibilities of using them as a renewable biosource to produce biodiesel. Under normal conditions, 15 microalgal isolates were tested for their lipid content. Oil content varied between 8 to 9.5percent DW in the diatom Melosira dubia to a range of 26.3 to 28.9percent DW in Nannochloropsis sp. However, higher lipid content can be induced through manipulation of culturing conditions by imposition of environmental and nutritional stress. Microalgae are also significant sources for bioactive primary and secondary metabolites. The antimycotic activity of five different microalgal strains were tested using three different extraction methods against five different plant pathogenic fungi. None of the isolates had any antimycotic activity however better sporulation and growth was recorded in the methanolic and filtrate I respectively. Three additional microalgal isolates were tested for their ability to induce resistance in cucumber seedlings against downy mildew of cucumber Pseudoperonospora cubensis.The experiments are still in progress; however plants treated with methanolic extracts showed higher vigor and a darker green color in comparison with other treatments.