Try this:
SELECT GROUP_CONCAT(DISTINCT a.ASSOCIATED_PROJECT_BASIC_INFORMATION_ID) AS Project_basic_information_ids ,
GROUP_CONCAT(DISTINCT b.TITLE) AS Project_titles
FROM MAP_ASSOCIATED_PROJECTS a
LEFT OUTER JOIN PROJECT_BASIC_INFORMATION b ON a.ASSOCIATED_PROJECT_BASIC_INFORMATION_ID = b.PROJECT_BASIC_INFORMATION_ID
WHERE a.PROJECT_BASIC_INFORMATION_ID = 'PBID_1'
GROUP BY a.PROJECT_BASIC_INFORMATION_ID