Change Align Export Title, Top Message and Bottom Message

How do I change align and font style for export title, top message and bottom message? The export title, top message and bottom message keep show in center when I export Excel or PDF file. Here is my code.

buttons: [
       {
              "extend": 'excelHtml5',
              "className": 'btn btn-table-excel',
              "init": function( api, node, config) {
                        $(node).removeClass('dt-button')
              },
              "title": exportTitle,
              "messageTop": exportMessageTop,
              "messageBottom": exportMessageBottom
       }, {
              "extend": 'pdfHtml5',
              "className": 'btn btn-table-pdf',
              "init": function( api, node, config) {
                       $(node).removeClass('dt-button')
              },
              "title": exportTitle,
              "messageTop": exportMessageTop,
              "messageBottom": exportMessageBottom
       }
],

My DataTables version is 1.10.13 and my DataTables Buttons version is 1.6.1