Transformation of 14C glucose and starch in soil

Abstract

To gain information about the breakdown and synthesis of carbohydrate, incubations of soil with 14C-stareh and 14C-glucose were studied under laboratory conditions. Carbon dioxide was liberated equivalent to 60–80 per cent of the substrate during incubation of soil with glucose (14 days) and with starch (84 days). The carbohydrate content of the hydrolysate of the substrate-soil mixture returned almost to the initial soil value within 35 days of incubation with 0.5 per cent starch, and within 7 days with 1 per cent glucose. The total glucose in the mixtures rapidly decreased but the amounts of other sugars present showed little change during incubation. To obtain the specific activities of sugars present in the hydrolysate various methods of separation were used including charcoal column, Celite column, and paper chromatography of the free sugars, and resin column chromatography of their borate complexes. With both substrates there was a rapid redistribution of 14C amongst the sugars. Galactose and mannose acquired considerable activity in all cases, rhamnose and fucose became labelled in one experiment, but arabinose and xylose were not labelled. This pattern of distribution remained unchanged with further incubation and glucose remained the most highly labelled sugar (70–80 per cent of total sugar radioactivity) for as long as the incubations were studied.