If your are running into a permissions issue, I suggest you look for a good permissions configuration to try to avoid using the bitnami user to run tomcat.
In case there is not any other way to solve that, please follow these steps:
sudo /opt/bitnami/ctlscript.sh stop tomcat
sudo chown bitnami:bitnami -R conf/ logs/ temp/ webapps/ work/
sudo /opt/bitnami/ctlscript.sh start tomcat
ps aux | grep tomcat