Process for fermentation of syngas

A process for starting a main fermentor for fermentation of syngas, the process comprising:

• inoculating a first culture of acetogenic bacteria into a seed reactor to provide a minimum initial viable cell density in the seed reactor of at least about 0.5 grams per liter;
• growing the culture of acetogenic bacteria with syngas to provide a cell density in the seed reactor of at least about 10 grams per liter;
• inoculating a first growth reactor with an inoculum from the seed reactor in an amount effective for providing a cell density in the growth reactor of at least about 0.5 grams per liter, wherein about 25% to about 75% of a volume of the seed reactor is inoculated into the first growth reactor;
• growing the culture with syngas to provide a cell density in the first growth reactor of at least about 10 grams per liter;
• inoculating a second growth reactor with an inoculum from the first growth reactor in an amount effective for providing a cell density in the growth reactor of at least about 0.5 grams per liter, wherein about 25% to about 75% of a volume of the first growth reactor is inoculated into the second growth reactor;
• growing the culture with syngas to provide a cell density in the second growth reactor of at least about 10 grams per liter;
• and
• inoculating a main fermentor with an inoculum from the second growth reactor in an amount effective for providing a cell density in the main reactor of at least about 0.5 grams per liter, wherein about 25% to about 75% of a volume of the second growth reactor is inoculated into the main fermentor,
• wherein a ratio of reactor volume to volume of a reactor receiving the inoculum is about 0.02 to about 0.5,
• wherein medium for each reactor is sent to a recycle filter to provide concentrated cells and permeate, wherein concentrated cells are returned to the reactor and permeate may undergo further processing.