Adsorption fermentation is also known as extractive fermentation. It is a technique in which products of the fermentation are removed from the broth by adsorption onto materials such as carbon or polymers.
Generally, the preferred method of doing this is to circulate the fermenting broth through the adsorbent substrate, because the fermentation products are often toxic to the microbes (yeast or bacteria) that are creating the fermentation.
Some of the information in this writeup was taken from the science dictionary at http://biotech.icmb.utexas.edu/; I oversaw the development of the dictionary (the website ceased being development in 1998) and believe I wrote the entry this writeup is partly or wholly based upon.