The present invention relates to novel esterases, more particularly to esterase variants having improved activity and/or improved thermostability compared to the parent esterase of SEQ ID N°1, SEQ ID N°2 or SEQ ID N°3 in acidic conditions and the uses thereof for degrading polyester containing material, such as plastic products. The esterases of the invention are particularly suited to degrade polyethylene terephthalate, and material containing polyethylene terephthalate in acidic conditions.