Evaluating the potential of local microalgae species for use as energy sources, nutritional supplements and biological control of plant pathogens -

Abstract

Microalgae are prokaryotic or eukaryotic photosynthetic microorganisms that have received lots of attention since the Second World War for their use potential as nutritional and renewable bioenergy sources. Their identification relied mainly on microscopy and chemical analysis. Recently, molecular identification is gaining importance and several primary and secondary barcode markers are being developed. In this study, 11 local isolates were isolated and successfully grown in culture media. Using primer pairs targeting the LSU and ITS of the ribosomal DNA, tuf Agene and mitochondrial cytochrome c oxidase 1 gene, the following genera were identified: Amphidinium cartera, Amphora sp., Chlorella vulgaris, Chloroidium saccharophilum, Leptolyngbya sp., Micractinium reisseri and Tetraselmis marina. Four selected isolates were studied for their lipid, pigments and protein contents. Micractinium sp, green algae contained the highest levels of all compounds tested. Its oil content varied between 14 and 16.5percent DW, 4.2percent DW omega FAs, with a chlorophyll content of 8µg-ml and a protein content ranging between 18.26 and 19.31percent. Among the isolates tested, Tetraselmis marina and the Jbd isolate Micractinium sp had the highest lipid content, saturated and monounsaturated fatty acids and thus seem most promising for a good quality biodiesel production. The antimycotic activity of four different microalgal strains were tested in-vitro using four different extracts against four different plant pathogenic fungi. None of the isolates showed promising antimycotic activity; however, better sporulation and growth was recorded in the non-methanolic and crude water extracts. Extracts of the Jbd microalgal isolate were also tested for their ability to induce resistance in cucumber seedlings against powdery mildew fungus, Sphaerotheca fuliginea. At the concentrations used, the extracts did not result in any significant control of powdery mildew fungus nor in growth improvement of cucumber plants. Further studies are recommended to isol