title: Growth and beta-galactosidase activity in cultures of Kluyveromyces marxianus under increased air pressure.
abstract: OBJECTIVE
  To investigate the effect of total air pressure raise on cell growth and intracellular beta-galactosidase activity in batch cultures of Kluyveromyces marxianus CBS 7894.
  
  
  RESULTS
  A pressurized bioreactor was used for K. marxianus batch cultivation under increased air pressure from 1.2 to 6 bar. Under these conditions no inhibition of cell growth was observed. Moreover, the improvement of the oxygen transfer rate (OTR) from the gas to the culture medium by pressurization led to an enhancement of the cell growth rate obtained at atmospheric pressure without aeration. The specific beta-galactosidase productivity increased from 5.8 to 17.0 U gCD-1 h-1 using a 6-bar air pressure instead of air at atmospheric pressure. The antioxidant enzyme superoxide dismutase (SOD) was slightly induced by the air pressure raise, which indicates that the defensive mechanisms of the cells can cope with an air pressure up to 6 bar.
  
  
  CONCLUSIONS
  These experiments showed that the increase of air pressure up to 6 bar is an alternative to other methods of preventing the oxygen limitation and can be applied in the beta-galactosidase production by K. marxianus.
  
  
  CONCLUSIONS
  The results here reported proved that, in what biological aspects are concerned, it is possible to use the air pressure increase as an optimization parameter of beta-galactosidase production in high-density cell cultures of K. marxianus strains.
authors: Centro de Engenharia Biológica - IBQF, Universidade do Minho, Largo do Paço, Braga Codex, Portugal.
authors: R
authors: R
authors: Pinheiro
authors: I
authors: I
authors: Belo
authors: M
authors: M
authors: Mota
mesh_terms: D000399:Air Pressure; D019149:Bioreactors; D004790:Enzyme Induction; D007716:Kluyveromyces / Q000201:enzymology* / Q000254:growth & development*; D013482:Superoxide Dismutase / Q000378:metabolism; D001616:beta-Galactosidase / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D013482:Superoxide Dismutase; D001616:beta-Galactosidase