For adding new options dynamically is neccesary to call clearOptions for clean the options, adding the new list options using addOption and call refreshState function after all.
    var listItems = [{id: 1, value: 'Element1'},{id: 2, value: 'Element2'}]
    /* Initialize select*/
    var $select = $('#element').selectize();
    var control = $select[0].selectize;
    control.clear()
    control.clearOptions();
    /* Fill options and item list*/
    var optionsList = [];
    var itemsList = [];
    $.each(listItems, function() {
      optionsList.push( {
                      value: this.id,
                       text: this.value
              });
       itemsList.push({
                     value: this.id,
                      text: this.value
                  });
     });
      
     /* Add options and item and then refresh state*/                    
    control.addOption(optionsList)
    control.addItems(itemsList);
    control.refreshState();
    /* Add element 1 selected*/
    $.each(result, function() {
        if (this.id == 1) {
        control.addItem(this.Tax.id,this.Tax.title);
         }
           
    });