Use of a Gluconobacter frateurii mutant to prevent dihydroxyacetone accumulation during glyceric acid production from glycerol.
ABSTRACT To prevent dihydroxyacetone (DHA) by-production during glyceric acid (GA) production from glycerol using Gluconobacter frateurii, we used a G. frateurii THD32 mutant, ΔsldA, in which the glycerol dehydrogenase subunit-encoding gene (sldA) was disrupted, but ΔsldA grew much more slowly than the wild type, growth starting after a lag of 3 d under the same culture conditions. The addition of 1% w/v D-sorbitol to the medium improved both the growth and the GA productivity of the mutant, and ΔsldA produced 89.1 g/l GA during 4 d of incubation without DHA accumulation.
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ABSTRACT: The considerable increase in biodiesel production worldwide in the last 5 years resulted in a stoichiometric increased coproduction of crude glycerol. As an excess of crude glycerol has been produced, its value on market was reduced and it is becoming a "waste-stream" instead of a valuable "coproduct". The development of biorefineries, i.e. production of chemicals and power integrated with conversion processes of biomass into biofuels, has been singled out as a way to achieve economically viable production chains, valorize residues and coproducts, and reduce industrial waste disposal. In this sense, several alternatives aimed at the use of crude glycerol to produce fuels and chemicals by microbial fermentation have been evaluated. This review summarizes different strategies employed to produce biofuels and chemicals (1,3-propanediol, 2,3-butanediol, ethanol, n-butanol, organic acids, polyols and others) by microbial fermentation of glycerol. Initially, the industrial use of each chemical is briefly presented; then we systematically summarize and discuss the different strategies to produce each chemical, including selection and genetic engineering of producers, and optimization of process conditions to improve yield and productivity. Finally, the impact of the developments obtained until now are placed in perspective and opportunities and challenges for using crude glycerol to the development of biodiesel-based biorefineries are considered. In conclusion, the microbial fermentation of glycerol represents a remarkable alternative to add value to the biodiesel production chain helping the development of biorefineries, which will allow this biofuel to be more competitive.Biotechnology for Biofuels 07/2012; 5(1):48. · 5.55 Impact Factor
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ABSTRACT: Spleen cells from mice with syngeneic tumor transplants are hyporesponsive in mixed-lymphocyte culture. The hyporesponsiveness is due to the activation of suppressor cells. Spleen from tumor-bearing mice, treated with mitomycin and added to normal mixed lymphocyte culture (with responding cells syngeneic to the added cells), inhibits proliferation of the responding cells. Suppressor activity in the spleen cells can be detected as early as 5 days after s.c. transplantation of P-815 mastocytoma into DBA/2 mice. Tumor cells placed in cell-impermeable i.p. diffusion chambers can also activate splenic suppressor cells. Suppressor cells can be activated in syngeneic mice by (DBA/2) P-815 cells, by (C3H) L25-cells, or by recent (C57BL/6) methylcholanthrene-induced tumors. The latter tumors retain their ability to activate suppressor cells after passaging in syngeneic mice. Only one tumor, induced with methylcholanthrene in DBA/2 mice, failed to activate suppressor cells. Suppressor activity in the spleen cells from mice with 20-day s.c. tumor transplants is not reduced after removal of glass-adherent cells. Suppressor activity is significantly decreased after removal of thymus-derived cells with anti-theta treatment and complement.Cancer Research 06/1978; 38(5):1269-73. · 8.65 Impact Factor
- 11/2011; , ISBN: 978-953-307-784-0