They appear to have given very vague information about what kind of bacteria they culture.
Assuming that they have told the truth and they feed their bacteria with carbon dioxide, dihydrogen and dioxygen, then those bacteria are not powered by the H2 with CO2 reaction (which is possible only in anaerobic conditions, by acetogenic or methanogenic bacteria/archaea), but by the oxidation of hydrogen.
The use of the word "fermentation" is completely inappropriate. Regardless what kind of bacteria they are using, the bacteria do not carry out any kind of fermentation (which refers to obtaining energy from large molecules, either by converting them into isomers or by breaking them down into smaller molecules).
In any case slowness is not their problem, because they do not use air as the source of CO2, but they use concentrated CO2, which accelerates a lot the CO2 capture.
Also, if the bacteria oxidize dihydrogen, they dispose of much more energy than the anaerobic bacteria which also capture CO2, so a doubling time of a few hours is believable.
What is unlikely is that they can produce their proteins at a cost comparable with, e.g., chicken meat or proteins extracted from legumes, when they use relatively expensive concentrated CO2 and dihydrogen to feed the bacteria and also a presumably expensive process to separate the protein and convert it into a product resembling meat.
Assuming that they have told the truth and they feed their bacteria with carbon dioxide, dihydrogen and dioxygen, then those bacteria are not powered by the H2 with CO2 reaction (which is possible only in anaerobic conditions, by acetogenic or methanogenic bacteria/archaea), but by the oxidation of hydrogen.
The use of the word "fermentation" is completely inappropriate. Regardless what kind of bacteria they are using, the bacteria do not carry out any kind of fermentation (which refers to obtaining energy from large molecules, either by converting them into isomers or by breaking them down into smaller molecules).
In any case slowness is not their problem, because they do not use air as the source of CO2, but they use concentrated CO2, which accelerates a lot the CO2 capture.
Also, if the bacteria oxidize dihydrogen, they dispose of much more energy than the anaerobic bacteria which also capture CO2, so a doubling time of a few hours is believable.
What is unlikely is that they can produce their proteins at a cost comparable with, e.g., chicken meat or proteins extracted from legumes, when they use relatively expensive concentrated CO2 and dihydrogen to feed the bacteria and also a presumably expensive process to separate the protein and convert it into a product resembling meat.