Bitterness is a flavor defect encountered in some cheeses and is responsible for reducing acceptability of cheeses. The objective of this study was to determine the effects of an adjunct culture, on removal of bitterness, microbiological, physico-chemical and proteolysis characteristic during 31-days ripening of Iranian white-brined cheese. Five batches of cheeses were prepared from pasteurized milk in duplicates and in three weeks interval. One batch was made with normal dose of milk clotting enzyme as control cheese(N), the second batch was made with three doses of milk clotting enzyme to produce bitter cheese(3N) and other three experimental batches were made with three doses of milk clotting enzyme plus L. helveticus CH-1 as adjunct culture. Adjunct culture was applied in three forms: on-shocked(3NH) and two forms of attenuated cultures, freeze-shocked(3NHFS) and heat-shocked(3NHHS). Microbiological and physico-chemical characteristics of cheeses such as pH, acidity, moisture, salt, fat and total protein content as well as texture hardness were measured during ripening. In addition, proteolysis was assessed during ripening by the terms of water soluble nitrogen (WSN), 12% trichloro acetic acid soluble nitrogen (TCA-SN) and total free amino acids (FAA). Also a taste panel group evaluated the cheeses at the end of ripening. The results of statistical analysis, showed that milk clotting enzyme concentration had no significant effect on compositional properties and the rates of proteolysis(P 0.05). But the effect of L. helveticus was remarkable on compositional characteristics. Adding L. helveticus decreased the pH(P 0.01) and increased the acidity(P 0.05) of cheeses significantly during two weeks and increased the moisture of cheeses but this was not significant during ripening period. The investigation of survival of L. helveticus indicated that the population of viable L. helveticus CH-1 was declined during ripening(P 0.05), but there was still a noticeable amount of this bacteria in cheeses after one month. The effect of adjunct culture on proteolysis characteristic was considerable. Although total protein declined during ripening in all cheeses(P 0.05), but the use of adjunct bacteria significantly caused more reduction. The level of water soluble nitrogen and 12% soluble nitrogen fractions were found to be significantly higher in the treatment involving L. helveticus (respectively P 0.05 and P 0.01). In term of total FAA, although adjunct culture affected the level of this parameter and it was higher in experimental cheeses than in the control, but it was not significant after one month ripening period. Organoleptic evaluations indicated among three treatments of L. helveticus , sample that included non-shocked culture caused more reduction of bitterness and enhancement of