@Copyright 1992 by The Humana Press Inc. All rights of any nature whatsoever reserved. 0273-2289/92/3603--0199502.40 A Biosensor for L-Proline Determination By Use of Immobilized Microbial Cells A. L. SIMONIAN, 1 E. I. RAININA, *'2 V. I. LOZINSKY, 3 i. E. BADALIAN, 1 G. E. KHACHATRIAN,1 S. SH. TATIKIAN, ~ T. A. MAKHLIS, 2 AND S. D. VARFOLOMEYEV 2 I Yerevan Physics Institute, Armenia; 2Chemical Enzymology Department of M. V. Lomonosov Moscow State University, Russia; and 3Institute of Food Substances, Russian Academy of Sciences, Moscow, Russia Received June 10, 1992; Accepted June 23, 1992 ABSTRACT A biosensor to quantify L-proline within 10-s-10 -3 mole/L con- cent-ration is described. Immobl]ized Pseudomonas sp. cells grown in a medium containing L-proline as the only source of carbon and nitrogen were used to create the biosensor. The cells oxidized L-proline specifically consuming 02 and did not react with other amino acids and sugars. The change in oxygen concentration was detected with a Clark oxygen membrane electrode. The cells were immobilized by en- trapment in polyvinyl alcohol (PVA) cryogel. The resultant biocatalyst had a high mechanical strength and retained its L-proline-oxidizing ability for at least two months. Index Entries: Pseudomonas sp.; L-proline-oxidizing activity; proline quantitation; immobilized cells. INTRODUCTION In recent years, remarkable progress has been made in designing ana- lyrical systems based on immobilized enzymes and cells. Such systems are used for the rapid and highly specific analysis of many organic com- pounds, including some amino acids (1,2). Compared to traditional *Author to whom all correspondence and reprint requests should be addressed. Applied Biochemistry and Biotechnology 199 Vol. 36, 1992