The present invention provides fatty acid synthetases which are responsible for novel fatty acid synthesis, polynucleotides which encode such fatty acid synthetases (e.g., a polynucleotide comprising (a) a polynucleotide consisting of the nucleotide sequence of Positions 1 to 12486 of SEQ ID NO: 1, or (b) a polynucleotide which hybridizes under stringent conditions to a polynucleotide comprising a nucleotide sequence complementary to the nucleotide sequence of Positions 1 to 12486 of SEQ ID NO: 1, and which encodes a protein having a fatty acid synthetase activity), expression vectors and transformants comprising such polynucleotides, methods for producing food and other products using such transformants, food products produced by such methods, and methods for assessing and selecting lipid-producing test fungi.