| The liquid spawn of Auricularia heimuer has many advantages and has been widely used in the cultivation and production of A.heimuer in recent years.At present,the research on the fermentation characteristics of A.heimuer liquid spawn mostly focuses on shake flask experiments,and there are few reports on production scale experiments and fermentation process studies.In this paper,the nationally recognized variety’Hei 29’（the name of the variety is’Heimuer 2’）was used as the test strain to study the effects of fermentation adjunct-sodium carboxymethyl cellulose（CMC-Na）on the physicochemical indexes and application effects of A.heimuer fermented mash.On this basis,the response surface method was used to optimize the shake flask medium formula and fermentation conditions.The 200 L fermentor was further used to study the changes of physicochemical indexes such as substrate nutrient consumption and mycelial growth during the fermentation of A.heimuer liquid spawn.The aim is to provide technical support and theoretical reference for improving the production quality and application effect of A.heimuer liquid spawn.The main results are as follows:（1）The effects of fermentation adjunct CMC-Na on the physicochemical indexes of A.heimuer fermented mash and its application in plate and cultivation bags were studied.The results showed that the addition of fermentation adjunct could significantly increase mycelial biomass,fermented mash viscosity and carboxymethyl cellulase activity（P<0.05）,which was helpful to improve the binding efficiency of fermented mash and substrate and the application effect of liquid spawn.When the addition concentration was3 g/L,the mycelial biomass and carboxymethyl cellulase activity were the highest,which were 12.50 g/L and 4.56 U/m L,respectively.When the addition concentration was 5 g/L,the diameter of mycelial bulb was the smallest,the viscosity of fermented mash and the wall hanging rate of substrate were the highest,which were 0.11 cm,39.34 m P·S and87.40%,respectively.In the process of mycelial growth,the activity of carboxymethyl cellulase was higher than that of other treatment groups when the concentration was 2 g/L or 3 g/L;when the concentration was 3 g/L,the biological efficiency was the highest,which was 101.40%.Pearson correlation analysis showed that mycelial biomass was significantly negatively correlated with mycelial bulb diameter（P<0.01）,laccase activity and p H（P<0.05）.Through comprehensive analysis,the optimum concentration of fermentation adjunct was determined to be 3 g/L.（2）Based on the addition of 3 g/L fermentation adjunct,the medium formula and fermentation conditions were optimized by response surface methodology.The results showed that the optimum formula was as follows:glucose 22.3 g/L,peptone 2.7 g/L,KH2PO4 2.0 g/L,Mg SO4·7H2O 1.5 g/L,mycelial biomass reached 13.22 g/L,which was27.89%higher than that before optimization.The optimum fermentation conditions were as follows:temperature 30°C,time 7 d,rotate speed 165 r/min,liquid volume 105m L/250 m L.The mycelial biomass reached 14.32 g/L,which was 38.53%higher than that before optimization.The variance analysis showed that the effect of medium formula on mycelial biomass was glucose>peptone>Mg SO4·7H2O>KH2PO4.The effect of fermentation conditions on mycelial biomass was temperature>liquid volume>rotate speed>fermentation time.The interaction between glucose and Mg SO4·7H2O,temperature and time,rotate speed and liquid volume was significant（P<0.05）.（3）The effects of fermentation adjunct,fermentation temperature and variable aeration on the physicochemical indexes such as substrate nutrient consumption and mycelial growth during the fermentation of liquid spawn and the application effect of cultivation were studied.The results showed that with the extension of fermentation time,mycelial biomass,viscosity of fermented mash,laccase activity and carboxymethyl cellulase activity showed an upward trend,mycelial bulb diameter,dissolved oxygen concentration,total sugar content,reducing sugar content and amino nitrogen content showed a downward trend,p H,TTC-dehydrogenase activity and CO2 concentration in exhaust gas of fermented mash showed a trend of increasing first and then decreasing.Increasing the fermentation temperature reduced the consumption rate of reducing sugar and amino nitrogen,and the mycelial biomass increased first and then slowed down.Under the condition of high aeration rate,the consumption rate of reducing sugar and amino nitrogen increased sharply,and the upward trend of mycelial biomass was first fast and then slow.The results of segmented ventilation experiment further showed that high aeration rate accelerated the consumption rate of reducing sugar and amino nitrogen.Pearson correlation analysis showed that mycelial biomass was significantly positively correlated with p H,CO2 concentration,viscosity,laccase activity and carboxymethyl cellulase activity（P<0.01）.Therefore,p H and CO2 concentration could be used as evaluation indexes for rapid determination of fermentation end point.TTC-dehydrogenase can be used as an evaluation index of strain activity.With the extension of fermentation time,the laccase activity of the same batch of liquid spawn increased,the ability to decompose lignin was enhanced,the germination time of mycelium was shortened,and the growth rate was accelerated.Under different treatment conditions,the mycelial biomass,laccase activity,carboxymethyl cellulase activity and TTC-dehydrogenase activity of increasing fermentation temperature were stronger than those of the control test,and the mycelial germination point increased and the activity increased,which was helpful to improve the cultivation and application effect of liquid spawn. |
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