NOVELTY - Preparation of 3'-thiosubstituted cephalosporin compound involves mixing 3'-thiosubstituted beta -lactam compound or its salt with D-4-hydroxyphenylglycine amide or an ester of D-4-hydroxyphenylglycine or D-phenylglycine amide or an ester of D-phenylglycine in the presence of a penicillin G acylase.    USE - For preparation of 3'-thiosubstituted cephalosporin compound, which is starting material for preparing cefoperazone or cefpiramide (claimed) used for the manufacture of medicament with antibacterial properties. The 3'-thiosubstituted cephalosporin compounds are used as beta -lactam antibiotics.    ADVANTAGE - The method is environmentally friendly and economical. The method facilitates rapid dissolution of starting material on the one hand while limiting the formation of side products, such as free side chain and thiols on the other hand. The method achieves highest conversions when the starting nucleus is dissolved in the reaction mixture. The method achieves highest yields of the product and lowest side reactions such as formation of thiols. The product formed is highly stable and pure thereby making it an excellent starting material for the high yield, high purity production of cefoperazone or cefpiramide.    DETAILED DESCRIPTION - A process for the preparation of 3'-thiosubstituted cephalosporin compound of formula (I) involves mixing 3'-thiosubstituted beta -lactam compound of formula (III) or its salt with D-4-hydroxyphenylglycine amide or an ester of D-4-hydroxyphenylglycine or D-phenylglycine amide or an ester of D-phenylglycine in the presence of a penicillin G acylase.    R1=a radical of formula tetrazol-5-yl (substituted on 1-position by R3) (iia), (1,2,3)triazol-4-yl (iib), (1,2,3)thiadiazol-5-yl (iic), (1,3,4)thiadiazol-5-yl (substituted on 2-position by R4) (iid), thiazol-2-yl (substituted on 4-position by CH3 and on 5-position by CH2CO2H) (iie) or 2-methyl-1,2-dihydro-(1,2,4)triazine-5,6-dione-3-yl (iif);    R3=CH3, CH2CO2H, CH2SO3H, CH2CH2OH or CH2CH2N(CH3)2;    R4=H or CH3;    R2=H or OH;    X=CH2, O or S.    An INDEPENDENT CLAIM is included for new crystalline form of compound (I) in which R1 is radical (iia), R3 is CH3 and R2 is OH and X is S, where the crystalline form of compound (I) has an XRD spectrum with peaks at 2 theta values of 13.9 plus minus 0.3, 19.1 plus minus 0.3, 28.1 plus minus 0.3, 32.2 plus minus 0.3 and 33.9 plus minus 0.3.