In the case of biotransformation of benzaldehyde to l-PAC (which is an intermediate of various α- and β-adrenergic drugs like ephedrine and pseudoephedrine) growing of the cell mass and biotransformation of benzaldehyde under regulatory conditions to obtain maximal cell mass and l-PAC are the main aims. Under normal fermentation conditions quantitative conversion of benzaldehyde into l-PAC has never been achieved [5] and [6]. Formation of l-PAC has been reported to be associated with the formation of by-products like benzyl alcohol, 1-phenyl-1,2-propanediol (PAC-diol) and benzoic acid. The present study aims at the scale-up of the biotransformation of benzaldehyde to l-PAC from shake flask to 5 l bioreactor with KLa as a scale-up criteria.