Executive Management

Aytaç Onkun was born in Gaziantep in 1974. He completed his undergraduate education in Anadolu University Faculty of Business Administration-Management Organization Department in 1998 and his graduate education in Toros University Faculty of Business Administration Social Sciences Institute in 2016.

In 1996, he started to work as a civil servant in Büyükşahinbey Agricultural Credit Cooperative affiliated to Gaziantep Regional Union of Agricultural Credit Cooperatives.

Appointed to Mersin Regional Union in 1997, Onkun worked in Erzin, Aydıncık and Anamur Agricultural Credit Cooperatives, respectively.

He was appointed as Director in 2008, Deputy Regional Director of Mersin Regional Union in 2012 and as Regional Manager.

Being appointed as Director in 2008 and then as Deputy Regional Manager of Mersin Regional Union and he afterwards worked as the Regional Manager Şanlıurfa Regional Union by 2019.

Mr. Onkun was appointed as a Member of the Board of Directors and General Manager (acting) on 10 June 2022.

After graduating from Boğaziçi University, Department of Business Administration in 1996, he started his career as Assistant Auditor at the independent audit firm KPMG. Afterwards, he served as Assistant Inspector at the CBRT Board of Inspectors for approximately one year between 1998 and 1999.

He worked as Financial Controller at Yibitaş Lafarge Cement Group between 1999-2002. After completing his military service, he started working for Turkish Airlines in 2003. He served as SPV, Accounting and Financial Control at Turkish Airlines between 2005-2016. Then, he worked as CFO at Borajet Airlines in 2017, and as Finance Director at the Northern Marmara Motorway between 2018-2020.

Hüseyin Bağrıyanık, who has been working as CFO at Tarım Kredi Holding since the beginning of 2021, has been continuing his duty at GÜBRETAŞ as Deputy General Manager (Finance) since 4 August 2021.

Mahmut Karaman graduated in 1990 from the Department of Mechanical Engineering, Yıldız Technical University. He received his master’s and doctoral degrees in control systems in the United States in 1997. He received his master of business administration (MBA) degree in 2007 from the University of Colorado, Boulder.

In 1998-2001, he worked at Hutchinson Technology, a significant company in the hard disk industry, and in 2001-2008 at Seagate Technology, the global leader in hard disk manufacturing. During that time, he taught courses at master’s level at the university in Colorado and Denver. In 2008-2013, he served as the Revenue Management Director at Turkish Airlines (THY) and Qatar Airways. In 2013-2015, he worked as the General Manager of Yıldız Technopark.

He started in GÜBRETAŞ in February 2015 as an Assistant General Manager responsible for Operations and Investments.

İbrahim Yumaklı graduated in 1992 from the Department of Management, Faculty of Economic and Administrative Sciences, Uludag University.

He started his work life in 1993 as an expert of import operations at Marshall Boya A.Ş., then served until 2011 as a manager in Marshall Boya A.Ş. within Akzo Nobel Türkiye and financial departments of group companies. In 2011, he transferred to Al-Jazeera Turkey, and managed Cine5 TV channel owned by Al-Jazeera Turkey in 2012-2015. In January-October 2016, he served as the International Operations Director of Anatolian News Agency.

Yumaklı started from October 2016 at GÜBRETAŞ as the Deputy General Manager and Executive Director, and was appointed as the General Manager on 5 May 2017.

Having received his master’s degree in finance from London Business School after receiving his Bachelor’s degree in Business Administration at Bosphorus University, Serttaş received certification as a Certified Public Accountant. After having started his career in the audit department of Arthur Andersen in 1996, he worked at the Istanbul, Johannesburg, London and Abu Dhabi offices of Arthur Andersen and Ernst & Young in financial audit and financial reporting areas. Then, he served as a General Manager consultant at IPIC in Abu Dhabi and as the founding CFO of the International Islamic Liquidity Management Company in Kuala Lumpur and Tosyalı Toyo Çelik A.Ş in Istanbul. He started working as an Assistant General Manager in charge of Finance at GÜBRETAŞ in September 2018.