2.4. Cyclic voltammetry
Cyclic voltammetry (CV) was performed using an electrochemical workstation (CHI 660D, Chenhua, Shanghai) equipped with three-electrode system. An Ag/AgCl electrode was used as the reference electrode, the anode as the counter electrode, and the cathode as the working electrode. Cyclic voltammograms were recorded at 55 °C or 30 °C at MG 262 low scanning rate of 2 mV/s.
2.5. Enzyme activity measurement
Dehydrogenase activity (DHA) was measured using triphenyl tetrazolium chloride (TTC) as a terminal proton acceptor as previously described (She et al., 2006). One DHA unit (U) was defined as the production of 1 μg of TPF per hour, and DHA was defined as U per milligram of protein (U/mg protein).
The activity of ATPase was determined as described by Zhang et al., 2014a and Zhang et al., 2014b and reported as U/mg protein, with one ATPase unit (U) defined as the production of 1 μmol of phosphorus from the decomposition of ATP. The protein content was measured using the Lowry method (Lowry et al., 1951).