Expression of vitreoscilla hemoglobin improves growth and levels of extracellular enzyme in yarrowia lipolytica

Abstract

Enhancement in oxygen uptake by high-celldensity cultivations has been achieved previously by expression of the bacterial hemoglobin gene from Vitreoscilla. The Vitreoscilla hemoglobin (VHb) gene was expressed in the yeast Yarrowia lipolytica to study the effect of expression in this commercially important yeast. The expression of VHb in this yeast was found to enhance growth, contrary to reported observations in wild-type Saccharomyces cerevisiae in which there was no significant growth enhancement. VHb-expressing Y. lipolytica exhibited higher specific growth rate, enhanced oxygen uptake rate, and higher respiratory activity. We report the beneficial effects of VHb expression on growth under microaerobic as well as under nonlimiting dissolved oxygen conditions. Earlier studies in Y. lipolytica have demonstrated inhibition of mycelia formation by respiratory inhibitors and poor nitrogen source, conditions poor for growth. VHb + Y. lipolytica cells were more efficient at forming mycelia, indicating better utilization of available oxygen as compared with the VHb À cells. Expression of VHb was also found to increase the levels of enzyme ribonuclease secreted into the medium, a property that may be beneficial for producing heterologous proteins in Y. lipolytica. B

Enhancement of Cellulose Pellicle Production by Constitutively Expressing Vitreoscilla Hemoglobin in Acetobacter xylinum

“…These results demonstrate that the presence of expressed VHb provided a growth advantage in A. xylinum, probably by bringing about an increase in the efficiency of O 2 uptake. The more efficient in O 2 uptake rate for VHb + than VHb -strains have been demonstrated elsewhere (30).…”

Constitutive expression of Vitreoscilla haemoglobin in Sphingomonas elodea to improve gellan gum production

“…1995; Roos et al. 2002; Bhave and Chattoo 2003; Suthar and Chattoo 2006; Liang et al. 2007), improvement of growth properties had been detected in various hosts with exogenous expression of VHb.…”

Co-production of S-adenosyl-L-methionine and L-isoleucine in Corynebacterium glutamicum

“…S. cerevisiae or P. pastoris could efficiently produce SAM because MAT activity encoded by SAM2 in these microorganisms is not inhibited by SAM, but the expensive L-methionine has to be added, thus raising the production cost. Overexpression of vgb, the gene encoding Vitreoscilla hemoglobin (VHb) could also improve SAM yield in P. pastoris [7], possibly because VHb had effects on the reduced oxygen availability, promoted cell growth and protein expressions [8][9][10], improved the electron transport chain, enhanced ATP synthesis rate and aerobic respiration efficiency [11][12][13]. In the H + -ATPase-defective mutant of Corynebacterium glutamicum ATCC 14067, the expression levels of pyk encoding pyruvate kinase, mqo encoding malate:quinine oxidoreductase, and mdh encoding malate dehydrogenase increased, contributing to the reoxidation of NADH during the increased respiration and enhanced glucose metabolism in response to cellular energy shortage [14]; 3-phosphoglycerate kinase encoded by pgk in glycolysis is also important for enhancing ATP substrate level phosphorylation [14].…”