Bioreactor (IMAGE) Penn State Caption Integral to the ability of biofilm reactors to produce vitamin K are specially designed internal plastic composite supports that microorganisms adhere to and on which they build intertwined colonies -- called biofilms -- that can withstand aeration and agitation needed to spur the microorganisms to secrete more vitamin K. These photos show the supports before fermentation (top), and after, covered by biofilms. Credit Ehsan Mahdinia/Penn State Usage Restrictions Non commercial use only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.