SUITABILITY OF COMMERCIAL BEET MOLASSES FRACTIONS AS SUBSTRATES FOR POLYHYDROXYALKANOATE PRODUCTION BY AZOTOBACTER-VINELANDII UWD

Beet molasses that had been fractionated commercially by ion exclusion resulted in two waste-streams: extract molasses (EM) and concentrated separator by-product (CSB). Only EM at 4-5 % w/v contained sufficient sugar to promote polyhydroxybutyrate (PHB) formation by Azotobacter vinelandii UWD, but the yield of PHB/protein was less than that obtained unfractionated beet molasses EM and especially CSB added at 0.5-2.0 % w/v to media containing a variety of sugar sources promoted an increased yield of PHB/protein. The best use of these beet molasses fractions was, therefore, as a minor addition to media containing sugars to increase PHB yield, but not as a primary substrate for PHB production.