Secretion of fatty acids by photosynthetic microorganisms

Abstract

Recombinant photosynthetic microorganisms that convert inorganic carbon to secreted fatty acids are described. Methods to recover the secreted fatty acids from the culture medium without the need for cell harvesting are also described.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims benefit of provisional application 61 / 007,333 filed 11 Dec. 2007. The contents of this application are incorporated herein by reference.TECHNICAL FIELD[0002]This invention relates to photosynthetic microorganisms that convert inorganic carbon to fatty acids and secrete them into the culture medium, methods of production of fatty acids using such organisms, and uses thereof. The fatty acids may be used directly or may be further modified to alternate forms such as esters, reduced forms such as alcohols, or hydrocarbons, for applications in different industries, including fuels and chemicals.BACKGROUND ART[0003]Photosynthetic microorganisms, including eukaryotic algae and cyanobacteria, contain various lipids, including polar lipids and neutral lipids. Polar lipids (e.g., phospholipids, glycolipids, sulfolipids) are typically present in structural membranes whereas neutral lipids (e.g., triacylglycerols, wax esters) ...

AI Technical Summary

Benefits of technology

The present invention is about improving the production of photosynthetic microorganisms that can produce fatty acids from inorganic carbon. The invention provides methods to remove the fatty acids from the culture medium without the need for cell harvesting, which lowers costs. The invention also enables the production of fatty acids of defined chain lengths, which can be used in various products like fuels and chemicals. The photosynthetic microorganisms used in the invention contain a recombinant expression vector that encodes an exogenous acyl-ACP thioesterase, which preferentially releases fatty acid chains containing 6 to 20 carbons from the ACP thioesters. The invention also includes a method to recover the secreted fatty acids and modify them for further use. Overall, this invention enables a more efficient and cost-effective way to produce fatty acids for various applications.

Problems solved by technology

Typically, eukaryotic microalgae are grown under nutrient-replete conditions until a certain cell density is achieved, after which the cells are subjected to growth under nutrient-deficient conditions, which often leads to the accumulation of neutral lipids.

Harvesting of the cells and extraction of the lipids are cost-intensive steps.

Further, there is no disclosure of converting inorganic carbon directly to secreted fatty acids using a photosynthetic organism grown in a culture medium containing inorganic carbon as the primary carbon source.

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