A new method for the formation of enzymatic chitosan membranes containing active cells of E. coli mutant producing L-aspartic acid was developed. Trisodium orto-phosphate as a gelation agent for the chitosan membrane formation was proposed. The highest productivity, with near 100% conversion of ammonium fumarate to L-aspartic acid, has been shown by the membranes characterized by a low permeate stream flow of 5-10 dm3/m2h at an overpressure of 0,05 MPa.