Microbial lipids from cellulolytic oleaginous fungus Penicillium citrinum PKB20 as a potential feedstock for biodiesel production

Abstract

Purpose: Microbial lipids derived from oleaginous fungi are considered as an alternative feedstock for biodiesel production. We attempt to isolate a cellulolytic oleaginous fungi as a potential feedstock for biodiesel production. Methods: The fungus was identified by 5.8 S-ITS rRNA gene sequencing. The extracellular enzyme activities were recorded after every 24 h for 7 days. Nile red staining and fluorescence microscopy was used to visualise the lipid bodies within the fungal hyphae. A renewable heterogeneous base catalyst derived from Musa balbisiana cola peels was used for the transesterification of Penicillium citrinum PKB20 derived oil into biodiesel. GC-MS analysis was used to analyse the fatty acid methyl esters (FAME) profile of the transesterified lipids. Results: Penicillium citrinum PKB20 was isolated from detritus rich soil of Assam, India. The endoglucanase, xylanase and β-glucosidase enzyme activities were found to be 292.83 ± 0.29, 111.72 ± 0.45 and 6.54 ± 0.13 U/mg respectively. The specific enzyme activity for extracellular lipase was found to be 3.12 ± 0.16 U/mg. It could accumulate up to 60.61% of lipids in nitrogen-limited medium (7.34 ± 0.45 g/L biomass production). The extracted lipids were converted to biodiesel with 89.3% conversion efficiency. The predominant fatty acids were oleic acid (30.09%), palmitic acid (20.25%) and linoleic acid (33.14%) suggesting a balance between oxidative stability and cold flow properties for suitable biodiesel quality. Conclusion: Penicillium citrinum PKB20 was found to be a potential feedstock for biodiesel production with desirable fuel properties. The cellulolytic nature could be utilised for simultaneous lipid production directly on cellulosic substrates.