Finally we were able to retrieve groups from account, setting value groupMembershipSearchDN in searchDNs entry for each iterateSearchFilter
<entry key="searchDNs">
<value>
<List>
<Map>
<entry key="groupMembershipSearchScope">
<value>
<List>
<Map>
<entry key="groupMemberFilterString"/>
<entry key="groupMembershipSearchDN">
<value>
<List>
<String>ou=UNIXGroups,ou=Groups,o=es</String>
</List>
</value>
</entry>
<entry key="objectType" value="posixgroup"/>
</Map>
</List>
</value>
</entry>
<entry key="iterateSearchFilter" value="(uid=*)"/>
<entry key="searchDN" value="ou=People,o=es"/>
<entry key="searchScope" value="SUBTREE"/>
</Map>
</List>
</value>
</entry>