Abstract: Methods of microbial screening for identifying alcohol acyltransferases for ester biosynthesis and submodules for ester pathways to produce butyryl-coenzyme A derived esters are disclosed. The method includes the introduction preselected plasmids into a respective host strain to form engineered microbes, in situ fermentation thereof followed by a colorimetric assay for quantification of production of the target ester. In situ fermentation includes inoculating each well of a microplate that have a culture media for producing target esters with one of the engineered microbes, adding an overlay of a solvent to each, and incubating the same. The colorimetric assay includes transfer of a quantity of the overlay from each well to respective clean wells of a new microplate, treatment of each well to form an iron-hydroxamic acid complex aqueous phase, centrifugation of the microplate, and measurement of the absorbance at 520 nm and comparison to a standard curve for the target ester.

Abstract: A modified chloramphenicol acetyltransferase comprising a tyrosine residue 20 having a phenylalanine (Y20F) mutation, a microorganism harboring the modified chloramphenicol acetyltransferase, and a method of producing ester by feeding the microorganism are disclosed. The method includes providing the microorganism harboring a modified chloramphenicol acetyltransferase in an environment suitable for the microorganism to produce an ester and feeding the microorganism (i) a sugar or a cellulose, and (ii) an alcohol and/or a carboxylic acid.

Abstract: An improved E. coli for carotenoid production comprising exogenous nucleic acids for expressing a carotenoid that the E. coli requires as necessary condition for the E. coli to reproduce. Some E. coli embodiments have diminished or abrogated expression of a gene in the group consisting of ldhA, frdA, poxB, pta, adhE, pykF, zwf, and maeB.