Ice Nucleation Active Bacterial Fermentation Process Optimization And Its Dynamics

Factors effecting growth and ice nucleation activity of INAPseudomonas syringae S940l were studied. The optima1 carbon sourcefor growth was surcose. but when using sorbitol or manitol as carbonsource, the ice nucleation activity of the bacteria1 strain S9401was stronger. The optimal nitrogen source for growth was N9801. Thebacteria1 strain S9401 was able to grow in pH 4.7～9.6 medium, thesuitable pH for growth was 7.5～8.5, when culturing in pH 7.7, theice nucleation activity was the strongest. The optima1 temperaturefor growth was 28～30℃, but above 26℃, the activity was destrotyed.High-level expression of ice-nuclei in this bactreium induced bylow temperature had been demonstrated.The fermentation process of INA bacterial strain S9401 wasoptimized by orthogonal test in a 10L stirred tank reactor (STR).A optimal fermentation medium and proper conditions were found,this medium contained sucrose as carbon source, N9801 as nitrogensource, K₃PO₄·3H₂O and microelements, and the initial concentrationof these components was 80g/L, 40g/L, 3g/L, 1mL/L respectively. Theconcentration of liquid seed was about 10%, initial pH value 7.0,dissolved oxygen≥24%, temperature 24℃, after 24h in a 10L STRcontaining 7～8L the fermentation medium, the cell mass reached18.1g dry cells/L. This fermentation process was tested andverified in a 2. 5m³ STR, and the fermentation characteristics ofthe INA bacterium strain S9401 had been analyzed.The kinetics of INA bacterial strain S9401 had also been studied.The governing equations of the mathematial model were given asfollows.dx/dt=μ_max((s₁-s₁₀)(s₂-s₂₀)/(k_s1+s₁)(k_s2+s₂))x ds₁/dt= (1/y_xs1)(dx/dt)+m₁xdt y-x-1 dts-1ds2 -- 1 de-- -- -- -- + m2xat yx, of.,/ .t2The initia1 condition for these equations were: t=0, x=x(),S 1 = S I", S2=S2('.These equat ions were numer i cal 1 y computed for the gi ven i ni t i a1condi t ions and tbe mode1 pardmeters were determi ned by opt im i zat ion.Calcu1ated resu1ts from the mode1 fitted with experimenta1 data.The arti'fica1 snowmaking tests showed that the 1NA bacteria1strain S940l was effective in enhancing the temperature range atwhich art if ical snow cou1d be generated, pro1onging snow conservedtime, increasing snow vol umes.