Step 1: Conversion of milk into curd.
When milk is converted into curd by lactic acid bacteria (Lactobacillus), there is an increase in certain vitamins.
Step 2: Vitamin synthesis.
The process enhances the amount of Vitamin B\textsubscript{12} due to microbial activity.
Step 3: Conclusion.
Thus, the vitamin content that increases is Vitamin B\textsubscript{12}.