Carbon limited cultures

Figure 2. Effects of carbon and nitrogen limitation on the production of LiP and MnP activities. Carbon limited cultures ( ) Nitrogen limited cultures ( ). Carbon limited cultures contained per liter 0.66 g diammonium sulfate and 2 g glucose. Nitrogen limited cultures were the same as the controls. They contained 0.2 g diammonium tartrate and 10 g glucose. All cultures received 11.2 ppm Mn(II).

The expression established by Pirt (1966) describes anaerobic systems and carbon-limited cultures. However, it gives a poor representation under substrate excess (Zeng and Deckwer, 1995a, 1995b). Then, Tsai and Lee (1990) built a model to represent the excessive consumption of substrate, under conditions of substrate excess (Equation 28). 

The mass balance equation and Y,/ and Yp, values erf corresponding carbon-limited cultures are then used to determine the carbon substrate and oxygen requirements for cell production. The yield of exopolysaccharide (corrected for cell production) is then compared to the thecsetical yield. The latter being calculated from the mean observed P/O quotient of carbon-limited cultures. 

Mashego, M., Van Gulik, W., Vinke, J., and Heijnen, J. 2003. Critical evaluation of sampling techniques for residual glucose determination in carbon-limited culture of Saccharomyces cerevisiae. Biotech. Bioeng. 83, 395-399. 

K. Yamane Yes, we do have cellulase production in carbon-limited cultures on glucose and xylose, and also on mannose and arabinose. ... 

C J l ratio, 67 caldum defidency, 142 caldum gluconate, 142,145 production of, 1 caldum hydroxide, 135 GOTdttii, 126,137,334 Candida brumptii, 138 Candida guilliermondii, 87 Candida lipolytica, 85 Candida utdis, 76,78,83,87 capital equipment, 26 capital expenditure, 26 capital investment, 21 caramelisation, 254 caraway, 238 caibapenems, 151,152 carbohydrates, 202 carbon balance, 256 carbon limited cultures, 50,56 carbojqrpeptidase A, 283 carrageenan, 287 carvone, 238 casein hydrolysate, 204 catabolism, 121 catalase, 143... 

These six strains can grow well in carbon-limited culture with WCO and 9—18 g/L lipid-rich biomass were obtained. Cellular lipids were accumulated signifi-cantiy in all cultures and produced oxalic acid up to 5 g/L. The highest Upid yield was determined in Aspergillus sp. ATHUM 3482, which accumulated Upid up to 0.64 g/g dry fungal mass with a yield of 0.74 g lipid per g fat (Papanikolaou et al., 2011). 

In practice, carbon limited chemostat cultures are used to estimate the P/O quotient These conditions are used because they favour the most efficient conversion of the carbon substrate into cellular material, ie the highest efficiency of energy conservation. The steady state respiration rate (qo,) is measured as a function of dilution rate (specific growth rate) and Yq can be obtained from the reciprocal of the slope of the plot. qo, is also known as the metabolic quotient for oxygen or the specific rate of oxygen consumption. 

The energetic requirements of exopolysaccharide production from various carbon sources can be calculated if the P/O quotient during growth on the carbon substrate is known. Table 3.1 shows molar growth yields measured during carbon limited growth in chemostat culture. 

The requirement for oxygen and carbon source for cell biosynthesis are calculated using nitrogen-limited mass balance equations for growth during exopolysaccharide production 01 res (nitrogen-limited cultures). These balances are derived from experimentally determined values of ... 

Carbon limiting is also used to encourage enzyme induction, place the population under selective pressure for degradation of recalcitrant substrates, and favor the simultaneous rather than sequential metabolism of a mixed carbon source.33 Carbon-limiting conditions can be achieved either through continuous culture (chemostat) or through a fed batch reaction. 

To perform fed-batch experiments with P. putida a method had to be developed to prevent carbon limitation and to prevent a buildup of the concentration of the fatty acids to inhibitory levels. HPLC methods to measure the concentration of aliphatic substrates and octanoic acid have been reported, but these are not suitable for the detection of long chain fatty acids in a watery phase due to their low solubility. Instead Huijberts et al. [55, 56] developed a method in which discrete pulses of fatty acids were added to fed-batch cultures. Substrate exhaustion was detected by a sudden increase in dissolved oxygen tension and this signal was used to trigger the injection of another fatty acid pulse into the... 

A comparison of alternative methods for producing this enzyme in batch and continuous culture is shown in Table III. The results are somewhat surprising. It was anticipated that in continuous culture under carbon-limited conditions the specific activity of maltase would be higher than observed in batch culture. However, for reasons that are not clear, the specific activity is substantially higher in batch culture. These results illustrate... 

Dauner, M., Storni, T, and Sauer, U. (2001) Bacillus suhtilis metabolism and energetics in carbon-limited and excess-carbon chemostat culture. 

---