Morphologically engineered strain of Aspergillus oryzae as a cell chassis for production development of functional lipids.

Cell morphology of the oleaginous fungus, Aspergillus oryzae BCC7051, was genetically engineered by disruption of non-essential genes involved in cell wall biosynthesis. Comparative phenotypic analysis of two disruptant strains defective either in α-1,3-glucan synthase 1 (ΔAoAgs1) or chitin synthase B (ΔAoChsB), and the wild type showed that the ΔAoAgs1 strain had no alterations in colonial growth and sporulation when grown on agar medium whereas the ΔAoChsB disruptant showed growth retardation and lower sporulation. However, tiny and loose pellets were found in the ΔAoAgs1 culture grown in liquid medium, where fungal pellet size was decreased by 35-50% of the wild type size. Further investigation of the ΔAoAgs1 mutant grown under stress-induced conditions, including high salt concentration, ionic strength and osmolarity, showed that its growth and development remained similar to that of the wild type. When cultivating the ΔAoAgs1 strain in a stirred-tank bioreactor, lipid production in terms of titer and productivity was significantly improved. As compared to the wild type, an increase of triacylglycerol and ergosterol contents with a proportional decrease in steryl ester content was observed in the ΔAoAgs1 strain. These results suggest that the morphologically engineered strain of A. oryzae is a robust cell chassis useful for exploitation in further production development of functional lipids with industrial significance.