Spent Sulfite Liquor

From NFWiki

As the name suggests, Spent Sulfite Liquor (SSL) is left over from the process of paper manufacturing where wood is digested to cellulose pulp with calcium bisulfite under heat and pressure. The liquid that is left over of this process is SSL.

SSL cannot be disposed of untreated because of the high biological demand. One alternative is to use this stream to grow torula yeast. The solids present in SSL are very low (10-12%) and only 20% of those solids are sugars comprising glucose, galactose, mannose, xylose and arabinose. The sugar content varies fromm the wood employed in paper manufacturing. For example, soft woods contain higher amounts of hexoses while hardwoods contain more pentoses. S.cerevsiae cannot process pentoses, and only torula yeast can readily digest both pentoses and hexoses.