Lactulose production from cheese whey using recyclable catalyst ammonium carbonate

• Cheese whey can be utilized as a cheap source for lactulose production.
• Ammonium carbonate can be applied as catalyst of weak alkaline reaction.
• Main product from lactose isomerization was galactose and lactulose.

Ammonium carbonate ((NH4)2CO3) was used as an alkaline catalyst of lactulose production from cheese whey. Maximum yield of 29.6% was obtained at reaction time of 28.44 min, (NH4)2CO3 of 0.76% at 97 °C. During reaction, (NH4)2CO3 was fully decomposed to NH3 and CO2, and these gases were recovered. To boost up NH3 recovery, various methods such as heating, aeration, and pH adjustment were applied. The optimal condition for the purpose of NH3 retrieval was temperature of up to 60 °C alongside aeration. Easy separation and recovery make (NH4)2CO3 a catalyst alternative to common alkaline chemicals especially for the weak alkaline reaction.