PURPOSE: To oxidize a glucide in high selectivity, high yield and high rate, by reacting an oxidized and fermented microbial cell entrapped and immobilized in a high polymeric gel with an alcohol or the glucide under pressurized oxygen atmosphere.

CONSTITUTION: An oxidized and fermented microbial cell is entrapped and immobilized in a natural polysaccharide, e.g. agarose, K-carrageenan or alginic acid. For example, the living microbial cell suspended in an aqueous solution of D-sorbitol is stirred with an aqueous solution of sodium alginate. The resultant mixture is then extruded into an aqueous solutin of calcium chloride to form fiber materials, which are then cut to a suitable length to give an immobilized microbial cell. The resultant immobilized microbial cell is then brought into contact with an alcohol, etc. under pressure of oxygen to oxidize the alcohol, etc. The above-mentioned method is applicable to the conversion of ethanol into acetic acid by Acetobacter aceti, conversion of D-sorbitol into L-sorbose by Gluconobacter suboxydans, etc.