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Looking for bioenergy in desert regions: Screening and cultivating lipid-producing microalgae from biological soil crusts


      Microalgal cultivation has received considerable attention because of increasing prominent energy depletion and environmental issues worldwide. However, most microalgae isolated from moderate environments currently cannot adapt well to the changing environmental conditions when cultivated at large scales. Therefore, microalgal diversity of biocrust from the extreme Tengger desert was investigated in this study, using high-throughput sequencing, for further exploring their abilities of lipid and biodiesel production. To identify the best management practices for cultivating biocrust microalgae on large scale, the light dependent growth kinetics and the corresponding lipid-producing properties were evaluated under different cultivation scales. The results of microalgal diversity decreasing with biocrust succession imply a large potential microalgal resource bank in the early developmental biocrusts. Through evaluating the light dependent growth kinetics of two screened microalgae Chlorella sp. BSC-24 and Monoraphidium dybowskii BSC-81, we verify that the screened biocrust microalgae could adapt well to the large cultivation scale with an increased light requirement. Furthermore, our results show that the variations of lipid productivity could be successfully interpreted by microalgal biomass accumulation (P<0.05), instead of lipid content (P>0.05). In particular, a quite good lipid productivity (18.36-18.78 mg·L-1·d-1) and fatty acid methyl ester compositions through microalgal lipid extraction and transesterification were achieved, via cultivating the screened biocrust microalgae in a 1000 L desert open raceway pond. Altogether, our results suggest screening and cultivating lipid-producing microalgae from biocrusts is a promising path to produce high quality of biodiesel for further industrial application in desert regions.