Yes, in the sense that you can acidify with lemon juice instead. No, in the sense that you can't use the same amount of lemon juice as citric acid and expect the same outcome. Lemon juice is 5-8% citric acid.
I would suggest using a buttermilk or buttermilk/yogurt starter if you want to make mozz. You will get more consistent results and better taste with lactic acid than citric.