Lactase was produced by Streptococcus salivarius subsp.
thermophilus grown on deproteinized whey. Maximum lactase
production in 6.85 per cent whey supplemented with certain
nutrients was 54.5 U/ml. Lactase was purified by ammonium
sulfate and acetone fractionation and gel filtration. It was
immobilized on chitin and chitosan by covalent binding. Lactase
immobilized on chitosan had the highest activity for hydrolysis
of whey lactose. The maximum amount of glucose produced by the
immobilized lactase was 20 per cent of lactose during conversion
of 71 per cent lactose in 6h. Xanthomonas campestris was able to
convert glucose, galactose, mixture of them, lactose, or whey to
xanthan, where the yield was 86, 67, 83, 2, and 1.8 per cent
respectively, after 72h in batch fermentation. When
deproteinized whey, which was hydrolyzed by immobilized lactase,
was used for xanthan production. The synthesis of xanthan was
generally as good as with comparable conventional media, the
yield reached to 65 per cent.