Characterization of oleaginous endophytic fungi of biodiesel plants as potential biofuel minifactories

Abstract

Fungi accumulate intracellular lipids in excess of their biomass. In the present study, endophytic fungi associated with plants that are used to produce biodiesel, namely, Jatropha curcas, Pongamia pinnata, Sapindus mukorossi, Mesua ferrea, Terminalia bellerica, Cascabela thevetia, and Ricinus communis were screened for total lipid production. The lipid content in the endophytic fungi Lasiodiplodia exigua SPSRJ27, Phomopsis sp. SPSRJ28, Pestalotiopsis microspora SPSRJL35, and Phomopsis sp. SPSRJL36, were found to be more than 20% of their dry biomass, an indicator of being oleaginous. Saturate, aromatic, resin, and asphaltene (SARA) analysis showed that L. exigua had the lowest amount of asphaltene weight percent, while Phomopsis sp. SPSRJL36 had the highest asphaltene stability. P. microspora contained the lowest sulfur content, higher heating value was found to be more than 35 MJ/kg in L. exigua, P. microspora, and Phomopsis sp. SPSRJL36, while Phomopsis sp. SPSRJ28 had a value less than 35 MJ/kg. L. exigua, Phomopsis spp., and P. microspora, when optimized for growth, showed a high amount of biomass and lipid content under static conditions. Significant differences (p < 0.05) in lipid content were observed among the fungal isolates L. exigua, P. microspora and Phomopsis spp. Genes of biomass-deconstructing carbohydrate-active enzymes (CAZys) showed variable banding patterns among the isolates. The present study revealed that the growth manipulation of oleaginous fungal endophytes opens up avenues for their larger exploration as biofuel minifactories.