Ethanol was a major byproduct of 2,3-butanediol (2,3-BD) fermentation by Klebsiella oxytoca ME-UD-3. In order to achieve a high efficiency of 2,3-BD production, K. oxytoca mutants deficient in ethanol formation were successfully constructed by replace the aldA gene coding for aldehyde dehydrogenase with a tetracycline resistance cassette. The results suggested that inactivation of aldA led to a significantly improved 2,3-BD production. The carbon flux to 2,3-BD was enhanced by eliminating the byproducing ethanol and at the same time reducing the accumulation of another byproduct acetoin. At last, by fed-batch culturing of the mutant, the final 2,3-BD titer up to 130 g/l with the productivity of 1.63 g/l.h and the 2,3-BD yield relative to glucose of 0.48 g/g was obtained.

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Fungal arachidonic acid (ARA)-rich oil is an important microbial oil that affects diverse physiological processes that impact normal health and chronic disease. In this article, the historic developments and technological achievements in fungal ARA-rich oil production in the past several years are reviewed. The biochemistry of ARA, ARA-rich oil synthesis and the accumulation mechanism are first introduced. Subsequently, the fermentation and downstream technologies are summarized. Furthermore, progress in the industrial production of ARA-rich oil is discussed. Finally, guidelines for future studies of fungal ARA-rich oil production are proposed in light of the current progress, challenges and trends in the field.

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