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A cytochrome aa3-type quinol oxidase from Desulfurolobus ambivalens, the most acidophilic archaeon (1994)

Anemüller, S. ; Schmidt, C.L. ; Pacheco, I. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

FEMS microbiology letters 117 (1994), S. 0

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ISSN: 1574-6968

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: Abstract Membranes of the extremely thermoacidophilic archaeon Desulfurolobus ambivalens grown under aerobic conditions contain a quinol oxidase of the cytochrome aa3-type as the most prominent hemoprotein. The partially purified enzyme consists of three polypeptide subunits with apparent molecular masses of 40, 27 and 20 kDa and contains two heme A molecules and one copper atom. CO difference spectra suggest one heme to be a heme a3-centre. The EPR spectra indicate the presence of a low-spin and a high-spin heme species. Redox titrations of the solubilized enzyme show the presence of two reduction processes, with apparent potentials of + 235 and + 330 mV. The enzyme cannot oxidize reduced cytochrome c, but rather serves as an oxidase of caldariella quinone. Due to their very simple composition, D. ambivalens cell appear as a promising candidate to study Structure-function relationships of cytochrome aa3 in the integral membrane state.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1574-6968.1994.tb06779.x

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d(−)lactic acid production by suspended and aggregated continuous cultures of Bacillus laevolacticus (1990)

Boer, Jan P. ; Teixeira, M. J. ; Neijssel, O. M.

Springer

Applied microbiology and biotechnology 34 (1990), S. 149-153

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ISSN: 1432-0614

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: Summary A new method of d(−)lactic acid production based on the aggregated form of growth of Bacillus laevolacticus in continuous culture in an anaerobic gaslift reactor is presented. With glucose as the substrate a bacterial dry weight of 25 g·1−1 and a lactic acid production rate of 13 g·1−1·h−1 was attained. In conventional glucose-limited chemostat cultures elevated levels of lactic acid stimulated specific lactic acid production while the formation rates of other end-products remained unaffected. In glucose-limited aggregated cultures lactic acid positively influenced the aggregation of cells, improving the volumetric production rate. It is concluded that lactic acid itself is a positive effector in the optimisation of lactic acid production with aggregated cultures of B. laevolacticus.