Martin Okos , professor of Food Engineering at Purdue University in West Lafayette,Ind.(phone 756-494-1211).uses fermentation to increase the value of food by-produces. One example is conversion of lactose found in cheese whey,the dilute liquid left after precipitation of milk solids,to alcohol,acetone butanol,and lactic acid.Lactiแ acid, in turn,can be polymerized into a “green” plastic ,I,e.one mads frome renewable resources