If you check your /etc/apache2/apache2.conf and look for User and Group:

# These need to be set in /etc/apache2/envvars
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}

Let’s replace User and Group variable in /etc/apache2/envvars.

export APACHE_RUN_USER=user-you-want-to-use
export APACHE_RUN_GROUP=user-you-want-to-use

Restart Apache.

sudo service apache2 restart

And you are done!