Homologous Overexpression of Diacylglycerol Acyltransferase in Oleaginous Fungus Mucor circinelloides WJ11 Enhances Lipid Accumulation under Static Solid Cultivation

Diacylglycerol acyltransferase (DGAT) catalyzes the binding
of
acyl-CoA to diacylglycerol to form triacylglycerol (TAG). Previous
studies strongly indicate that DGAT2, rather than DGAT1, is crucial
for TAG accumulation in the oleaginous fungus Mucor
circinelloides. To increase the lipid content of M. circinelloides WJ11, McDGAT2 was overexpressed
by homologous recombination; compared to the control strain Mc2075,
transformants McDGAT2d showed a significant increase in biomass for
both spores and mycelia (from 87.7 to 101.2 mg/g in spores and from
75.6 to 93.1 mg/g in mycelia). McDGAT2 overexpression under static
solid fermentation gave a greater boost to lipid accumulation in mycelia
than in spores. Total fatty acid content in mycelia increased by 68.0%
(from 13.6 to 22.8%) and in spores by 26.3% (from 10.6 to 13.4%).
However, under submerged fermentation, the lipid content of McDGAT2d
was the same as the control, while biomass was slightly reduced. Transcriptomics
showed that NADPH was derived mainly from the pentose phosphate pathway,
acetyl-CoA was from multiple pathways, and leucine metabolism played
an important role in substrate supply for fatty acid biosynthesis.
Static solid fermentation may be the more suitable fermentation method
for microbial oil production by filamentous fungi due to its lower
fermentation costs.