Sucdnoglycan

Carbohydrate Net ATP produced/unit sucdnoglycan Rate of sucdnoglycan production (g g h 1)... 

Table 3.2 Rates of sucdnoglycan synthesis from carbohydrates and net ATP production during synthesis. Data obtained from Linton J. D. (1990) FEMS Microbiology Reviews 75,1-18.

In the sucdnoglycan fermentation, exopolysaccharide production commences after cessation of growth. During the 80 hour production phase of the fermentation, there is a linear increase in product concentration and a linear decrease in residual glucose. 

Explain briefly why the rate of xanthan production increases during the production phase while that of sucdnoglycan remains constant... 

Explain why it would be inadvisable to use the carbon source as growth limiting nutrient in the sucdnoglycan fermentation. 

In the sucdnoglycan fermentation, what is the growth yield coeffident for ammonia (in units of g g"1 molecular weight of ammonia = 17). 

Class 1 or 2, depending on the substrate used. We can see from Table 2, for example, that sucdnoglycan biosynthesis leads to a net production of ATP (Class 2) with ethanol as substrate, but the biosynthesis is energy requiring (Class 1) with glucose as substrate. 

Xanthan is synthesised during exponential growth of the culture, whereas sucdnoglycan is synthesised after growth has ceased (biomass constant). 

Since sucdnoglycan synthesis commences after the growth phase there would be no carbon available for sucdnoglycan formation. 

Glucose limits sucdnoglycan production (ammonia limits growth). It is necessary to limit sucdnoglycan production to avoid an excessively viscous fermentation liquor which would affect mixing and subsequent downstream processing to recover exopolysaccharide. 

---