The concentration of formate was quantified with a high-performance liquid chromatography (HPLC) system equipped with a photodiode array detector (SPD-M40, Shimadzu). An Aminex HPX-87H column (300×7.8 mm, BIO-RAD) was used at 30 °C. 5 mM of sulfuric acid was flowed as the eluent at the rate of 0.6 ml min -1 . A chromatogram of formate is presented in SI Appendix, Fig. with the obtained calibration curve.