Results of prebiotics addition (3% inulin and 3% lactulose), yoghurt starter producing expolysaccharides (EPSYS) and transglutaminase (TGase, 0.07%) revealed that the fermentation of bio-yoghurt samples containing inulin and lactulose lasted shorter than fermentation of EPSYS - and TGase -contained samples as well as control.  Inulin and lactulose resulted in slightly higher acidity (after overnight cooling) than fresh control without additives then, the acidity gradually increased with different rates during cold storage for all samples. The pH showed an opposite trend for that of acidity. The lowest pH values were recorded for inulin and lactulose- treated fresh samples, whereas the pH gradually decreased with different rates during storage. Fresh bio-yoghurt with inulin and TGase had the highest curd tension values compared with all samples while those containing inulin showed the highest significant values after 5 and 10 days of storage. Concerning curd syneresis (CS), the fresh samples made with inulin had the lowest significant CS, while the differences among the rest treatments were insignificant. The differences among the treated samples of 5 days age were insignificant and were significantly lower than those of the control, which showed the highest value after 10 days of storage. Addition of inulin and lactulose significantly increased the viability and counts of Lb. delbruekii spp. bulgricus and B. bifidum bacteria at any given storage time. On the tenth day of storage, the counts of Lb. delbruekii spp. bulgricus showed a sharp decline which was significantly different (P<0.05) from the initial counts. It was also found that adding inulin and lactulose were the best in increasing survival and counts of bifidobacteria followed by the samples containing EPSYS and TGase in order. Sensory evaluation showed that using inulin and lactulose improved body, texture and flavour compared with bio-yoghurt without additives and manufactured with adding TGase. So, this study recommended using inulin and lactulose for their functional properties to guarantee the existence of bifidobacteria with suitable counts in bio-yoghurt to gain its healthy benefits.