Optimization of C/N ratio preparation of protein-rich and multi-enzymes feed thallus through synergic fermentation of mixed distillers' grains

A new procedure of determining optimal C/N (the rate of carbon source to nitrogen source) of mixed distillers' grains for combined bacteria synergic fermentation is established. At the same time an improved method evaluating bacteria growth, called method of dry cell weighing by filtering is developed. For each combination of C and N, their initial and residual contents before and after fermentation respectively are determined. Then followed the calculation of utilization of C and N sources by the compound bacteria. The optimal C/N is finally located from among the utilization of C and N of several combinations and the weight of produced mass of oven-dried thallus. The conditions of fermentation are: inoculum size 10%, temperature 30.0 degrees C, rotational speed 170 r/min, shake culture time 48 h. The best results obtained from orthogonal experiments are: maximum mass of oven dried thallus is 14.693 g in a liter liquid medium, maximum utilization rate of carbon source is 98.13% and maximum utilization rate of nitrogen is 78.14%. Optimal C/N is 5.1.