AMPNI and Aegean Oil

Melissanidis was the founder and owner of the marine fuels and bunkering services supplier Aegean Marine Petroleum Network Inc. (AMPNI)^[16] and of the petroleum company Aegean Oil which he still currently owns. He launched the business in 1995. In August 2016, Melissanidis sold all the shares of AMPNI.^[10]

In 2017 Melissanidis attempted to return to AMPNI, through a proposed acquisition of Hellenic Environmental Center, a company owned by the Melissanidis family, by AMPNI. The reaction of a group of ‘activist’ minority shareholders,^[17] led to the cancellation of this deal, changes in AMPNI's board and an internal investigation by the board's audit committee that discovered the misappropriation of up to $300 million in assets.^[18] The investigation found that a set of shell companies, fake receipts and documents covered up the misappropriation making it look like Aegean had legitimate contracts with customers that would explain the missing cash.^[19][20] AMPNI filed for Chapter 11 bankruptcy and was acquisitioned by the Mercuria group,^[21] and operates as Minerva Bunkering.^[22] AMPNI's creditors have filed suits against Melissanidis in courts in the US^[23] and Luxemburg^[24][25][26] accusing Melissanidis of fraudulent activities,^[27][28] of destroying evidence (including the use of military grade deletion software) and of threatening witnesses.^[29] Melissanidis has denied these allegations^[30] but decision is awaited in regards to these suits.

AEK Athens Football Club

Melissanidis was President of AEK Athens F.C. during the 90's.

On June 7, 2013, Dimitris Melissanidis became again active for AEK, after they declared bankruptcy, in order to save the club and bring them back to success. The company declared bankruptcy and were relegated to Greece's third tier. The club was reported to owe €170 million ($219 million) in taxes and will start the 2013–14 campaign in the Football League 2, the country's third amateur division.^[31] Later, together with other notable AEK fans and old players, they created the non-profit association "Union Friends of AEK" (Enosi Filon AEK) which took the majority stake of the football club.^{[citation needed]}

Since the arrival and return of Melissandis to the club, AEK has secured major sponsorship deals which will give the club a huge financial boost. Melissanidis has secured a €2.1 million sponsorship deal from OPAP, a €1.5 million contract with Greek Telecommunications company Nova Sports and a €1 million sponsorship deal with Fujitsu.^{[citation needed]}

Melissanidis has unveiled plans also for a new stadium in Nea Filadelfia, where the old stadium of AEK was placed.^[32][33]

On October 2, 2013, the AEK Athens board, under Dimitris Melissanidis, presented plans for the new stadium to the municipality of Nea Filadelfeia, in order to gain permission to build. A new 4-star UEFA system stadium will be built, seating between 32,500 and 35,000 spectators. The cost of this project is estimated to be around €70-80 million. It is modelled after the Agia Sophia church in Constantinople, as AEK has its roots there. Around 1,500-2,000 new jobs will become available and the neighbourhood is expected to benefit largely from this endeavour.^[34] The structural design of the stadium was designed by Italian architect Massimo Majowiecki and the architectural design by the Greek architect Athanasius Kyratsous. Majowiecki is most known for designing the home ground of the Juventus Stadium.^[35]

Emma Delta & OPAP

Melissanidis, via his own company Geonama Holdings,^[36] reported owned a stake in Emma Delta, a private equity fund of EMMA Capital. Emma Delta acquired 33% stake of Greek betting firm OPAP^[37] for €652 million.^[36] According to Reuters, OPAP was the European biggest betting firm, as of 2008.^[38] Dimitris Melissanidis is a major shareholder in OPAP and is the largest investor, investing €157 million in the takeover.^[39]

At the signing, Dimitris Melissanidis ended his statement by commenting that "OPAP is turning a page".^[40]

On 18 February 2022 it was announced that the Melissanidis family had sold its entire stake in OPAP to Allwyn, owned by Czech billionaire Karel Komarek, for a price of EUR 327.4 million.^[41] This development is not unrelated to the lawsuits that Mr. Dimitris Melissanidis, his son George Melissanidis and their companies are facing in connection with Aegean Marine Petroleum Network, especially since Allwyn has announced its plans to publicly list on the New York Stock Exchange (NYSE), working in partnership with special purpose acquisition company Cohn Robbins Holdings Corp. (CRHC).^[42][43]