Abstract: Increasing space-time-yield, carbon-conversion-efficiency and carbon substrate flexibility in the production of fine chemicals The inventors of the current invention have found a surprising positive effect of increased cAMP levels and/or manipulating the PTS system on the space-time-yield, carbon-conversion-efficiency and carbon substrate flexibility of fine chemical production of a host organism. This was achieved by de-regulating adenylate cyclase cyaa by deleting the C-terminal regulatory region leading to increased cAMP levels or deleting the Crr protein activity (carbohydrate repression resistance) which regulates the carbohydrate utilization system. Both lead to increased 2-fucosyllactoe and 6-sialyllactose production (human milk oligosaccharides) and increase carbohydrate usage.

Abstract: Described herein are microorganisms, in particular yeast, which have been transformed with one or more expression construct(s) for i) the overexpression of the native genes encoding xylulose kinase (XKS1), transaldolase (TAL1), transketolase 1 (TKL1) and transketolase 2 (TKL2) and ii) the expression of a functional heterologous gene encoding a xylose isomerase (XI), where the xylose isomerase (XI) gene is derived from a microorganism selected from the group consisting of T. neapolitana, A. andensis and C. clariflavum. Also described herein are expression constructs, methods for fermenting pentose sugars using the microorganisms and methods for producing such microorganisms.