PubMed · 15286767
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Aparna Surendran. 2004. The virtuous virus.. https://doi.org/10.1038/nm0804-767
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Biomolecular motors, in particular motor proteins, are ideally suited to introduce chemically powered movement of selected components into devices engineered at the micro- and nanoscale level. The design of such hybrid "bio/nano"-devices requires suitable synthetic environments, and the identification of unique applications. We discuss current approaches to utilize active transport and actuation on a molecular scale, and we give an outlook to the future.
A carotenoid-accumulating bacterium isolated from soil, identified as a Sphingomonas sp., grew at 0.18 h(-1) and produced 1.7 mg carotenoids g(-1) dry cell, among which beta-carotene (29% of total carotenoids) and nostoxanthin (36%). A mutant strain, obtained by treatment with ethyl methanesulfonate, accumulated up to 3.5 mg carotenoids g(-1) dry cell. Accumulation of beta-carotene by this strain depended on the oxygenation of the growth medium, with maximal accumulation (89%) occurring under limiting conditions. Beta-carotene accumulation could be further enhanced by incubating the cells in the presence of glycerol (either not or only slowly assimilated) and yeast extract resulting in an accumulation of 5.7 mg beta-carotene g(-1) dry cell wt. The strain used lactose as carbon source with similar biomass and carotenoid production, providing a viable alternative use for cheese whey ultra-filtrate.
To obtain a mannitol-producing Lactococcus lactis strain, the mannitol 1-phosphate dehydrogenase gene (mtlD) from Lactobacillus plantarum was overexpressed in a wild-type strain, a lactate dehydrogenase(LDH)-deficient strain, and a strain with reduced phosphofructokinase activity. High-performance liquid chromatography and (13)C nuclear magnetic resonance analysis revealed that small amounts (<1%) of mannitol were formed by growing cells of mtlD-overexpressing LDH-deficient and phosphofructokinase-reduced strains, whereas resting cells of the LDH-deficient transformant converted 25% of glucose into mannitol. Moreover, the formed mannitol was not reutilized upon glucose depletion. Of the metabolic-engineering strategies investigated in this work, mtlD-overexpressing LDH-deficient L. lactis seemed to be the most promising strain for mannitol production.