The present invention is directed to isolated nucleic acid molecules and polypeptides of thraustochytrid polyunsaturated fatty acid (PUFA) synthases involved in the production of PUFAs, including PUFAs enriched in docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), or a combination thereof. The present invention is directed to vectors and host cells comprising the nucleic acid molecules, polypeptides encoded by the nucleic acid molecules, compositions comprising the nucleic acid molecules or polypeptides, and methods of making and uses thereof.

The disclosure relates to the field of specialty chemicals and methods for their synthesis. In embodiments, the disclosure provides viable bacterial cells which comprise heterologous dual 3-hydroxy-acyl-ACP dehydratase/isomerases, etc. The disclosure further provides monounsaturated fatty acid derivative molecules produced by the viable bacterial cells which are non-native to the bacterial cells. The disclosure further provides methods for the preparation and production of non-native monounsaturated fatty acid derivative molecules such as e.g., an 3-monounsaturated fatty acid derivative, an 5-monounsaturated fatty acid derivative, an 9-monounsaturated fatty acid derivative, an 11-monounsaturated fatty acid fatty acid derivative, etc.

Microorganisms are genetically engineered to continuously produce fatty acids, fatty alcohols, cultured protein, or any combination thereof by microbial fermentation, particularly by microbial fermentation of a gaseous substrate. The microorganisms are C1-fixing. The production of fatty acids, fatty alcohols, and cultured proteins can be improved. This can be improved through the expression of 3-hydroxyacyl-ACP:CoA transacylases.

Provided are non-natural or variant -ketoacyl-acyl carrier protein (ACP) synthase (KAS) IVa enzymes (KASIVa), polynucleotides encoding such variant KASIVa, host cells expressing such variant KASIVa, oils and oil products produced by such cells, and methods of making and using such variant KASIVa.