Influence of oxygen and substrate supply on the metabolism of Candida maltosa during cultivation on n-alkanes

Abstract

The influence of different states of oxygen and alkane substrate supply on the metabolism of Candida maltosa during cultivation on n-alkanes has been investigated. At sufficient oxygen and substrate supply a nearly equimolar ratio between the formation of biomass and alkane oxidation was observed. About 45% of the carbon source utilized was incorporated into the biomass. Strong oxygen limitation decreased protein formation and carbon incorporation into the biomass with a simultaneous increase in CO2 formation, whereas periodic changes of oxygen supply only caused a decrease in carbon incorporation into the biomass and an increase in CO2 formation. During cultivation in the presence of an inert hydrocarbon (pristane) it was found that carbon limitation and oxygen saturation diminished the formation of total and nitrogen-containing biomass, whereas carbon and oxygen limitation reduced the formation of total biomass.

Candida maltosa

“…Under nitrogen limitation conditions, the crude protein content (up to 17-23%) and the nucleic acid (3-4%) content of alkane-grown cells decreased strongly, connected with an increase of both lipid (28-30%) and total carbohydrate (38-44%) contents (Bruckner and Troger 1981a,b;Gradova et al 1983). Comparable results were obtained to some extent also under oxygen limitation conditions (Riege et al 1989). These data for C. maltosa are in agreement with results obtained with other hydrocarbon-utilizing Candida yeasts (Nabeshima et al 1970;Kiippeli et al1975;see Bruckner and Troger 1981b) and with the protein content known for S. cerevisiae (Gradova et al 1983).…”

“…Additionally, several studies were also performed with C. maltosa at the biochemical level, showing regulation by the oxygen supply not only on the growth rate but also on biomass yield, biomass composition, and the content of enzymes involved in alkane degradation (Davidov and Gololobov 1980a,b;Mauersberger 1985;Wiedmann et al , 1988aSchunck et al 1987a,b;Riege et al 1989;Ilchenko et al 1989;Shilova et al 1989;cf. also Sects.…”

“…• under the influence of perturbations, like substrate or oxygen limitations, which occur in industrial recirculation reactors used for SCP production on alkanes, as well as under the influence of alternating milieu changes as substrate (glucose, sucrose, or n-alkanes) and oxygen supply during cultivation in laboratory or industrial fermenters (Glombitza and Heinritz 1979;Heinritz and Bley 1979;Heinritz et al 1981Heinritz et al , 1985Glombitza 1982;Riege et al 1989;Zentgraf 1991aZentgraf ,b,c, 1993);…”

“…Strong oxygen limitation decreased protein formation and carbon incorporation into the biomass with a simultaneous increase in CO 2 formation, whereas periodic changes of oxygen supply caused a decrease only in carbon incorporation into the biomass and an increase in CO 2 formation, but not the incorporation into the nitrogen-containing biomass (protein), probably due to the presence of different regulation sites in the cell. For the industrial SCP production from crude oil fractions in recycle reactors, these results show that periodic oxygen gradients can cause lower yield coefficients (g biomass/g substrate) and higher CO 2 formation, whereas the protein formation per g utilized substrate might remain constant (Riege et al 1989). Included in these investigations for optimizing biomass production with C. maltosa was the concept of using mixed substrates or auxiliary substrate concept (Babel 1979(Babel , 1980.…”

“…It has been demonstrated that nonhomogeneity of the oxygen concentration in the culture medium during continuous cultivation on crude oil fractions or n-alkanes diminished the biomass production efficiency of C. maltosa (Heinritz et al 1985;Riege et al 1989). Strong oxygen limitation decreased protein formation and carbon incorporation into the biomass with a simultaneous increase in CO 2 formation, whereas periodic changes of oxygen supply caused a decrease only in carbon incorporation into the biomass and an increase in CO 2 formation, but not the incorporation into the nitrogen-containing biomass (protein), probably due to the presence of different regulation sites in the cell.…”