A method for producing a biomass comprising at least 65% protein of total biomass by dry weight from hydrogen-oxidising microorganisms comprising bacteria selected from the genus Cupriavidus sp, using one or more input streams comprising one or more gaseous substrates, comprising hydrogen and oxygen, the method comprising: contacting the microorganisms in a liquid phase with a nutrient composition comprising nitrogen and phosphorous-comprising compounds and the gaseous substrates, wherein the one or more gaseous substrates comprises carbon dioxide, or wherein the nutrient composition comprises carbon-comprising compounds, and wherein the input stream and nutrient composition are controlled and wherein the biomass is produced at a rate of more than 10 g/l/d, the method further comprising: i. controlling the input stream comprising adding a molar ratio of hydrogen: oxygen to the liquid phase of from 1: 1 to 10: 1; ii. controlling the input stream and nutrient composition comprising maintaining a specific growth rate of the microorganisms of from 1.0 to 8.0 d -1 or from 0.04 to 0.3 h -1; iii. controlling the input stream comprising maintaining hydrogen at a transfer rate of from 0.03 to 1.2 mol/l/h in the liquid phase and/or oxygen at a transfer rate of from 0.003 to 0.4 mol/l/h in the liquid phase; iv. controlling the input stream comprising maintaining a molar ratio of hydrogen: oxygen gas hold-up in the liquid phase of from 0.5: 1 to 7: 1, v. controlling the input stream and nutrient composition comprising maintaining a concentration of the microorganisms in the liquid phase of the bioreactor of at least 10 g/l, and vi. replacing the liquid phase of the bioreactor where the microorganisms are grown and maintained at a volume of from 4 to 30% per hour. contacting the microorganisms in a liquid phase with a nutrient composition comprising nitrogen and phosphorous-comprising compounds and the gaseous substrates, wherein the one or more gaseous substrates comprises carbon dioxide, or wherein the nutrient composition comprises carbon-comprising compounds, and wherein the input stream and nutrient composition are controlled and wherein the biomass is produced at a rate of more than 10 g/l/d, the method further comprising: i. controlling the input stream comprising adding a molar ratio of hydrogen: oxygen to the liquid phase of from 1: 1 to 10: 1; ii. controlling the input stream and nutrient composition comprising maintaining a specific growth rate of the microorganisms of from 1.0 to 8.0 d -1 or from 0.04 to 0.3 h -1; iii. controlling the input stream comprising maintaining hydrogen at a transfer rate of from 0.03 to 1.2 mol/l/h in the liquid phase and/or oxygen at a transfer rate of from 0.003 to 0.4 mol/l/h in the liquid phase; iv. controlling the input stream comprising maintaining a molar ratio of hydrogen: oxygen gas hold-up in the liquid phase of from 0.5: 1 to 7: 1, v. controlling the input stream and nutrient composition comprising maintaining a concentration of the microorganisms in the liquid phase of the bioreactor of at least 10 g/l, and vi. replacing the liquid phase of the bioreactor where the microorganisms are grown and maintained at a volume of from 4 to 30% per hour. i. controlling the input stream comprising adding a molar ratio of hydrogen: oxygen to the liquid phase of from 1: 1 to 10: 1; ii. controlling the input stream and nutrient composition comprising maintaining a specific growth rate of the microorganisms of from 1.0 to 8.0 d -1 or from 0.04 to 0.3 h -1; iii. controlling the input stream comprising maintaining hydrogen at a transfer rate of from 0.03 to 1.2 mol/l/h in the liquid phase and/or oxygen at a transfer rate of from 0.003 to 0.4 mol/l/h in the liquid phase; iv. controlling the input stream comprising maintaining a molar ratio of hydrogen: oxygen gas hold-up in the liquid phase of from 0.5: 1 to 7: 1, v. controlling the input stream and nutrient composition comprising maintaining a concentration of the microorganisms in the liquid phase of the bioreactor of at least 10 g/l, and vi. replacing the liquid phase of the bioreactor where the microorganisms are grown and maintained at a volume of from 4 to 30% per hour.