Turkey raided 44 companies in Istanbul, as part of a post-coup crackdown, and also applied pressure on a second front, with a court ordering shut Ozgur Gundem, a major pro-Kurdish newspaper.
Akfen Holding, a firm focused on technologies, was one of the hardest hit by the raids, state broadcaster TRT reported, with its chairman among the 50 people detained.
The 19-year-old company is allegedly linked to preacher Fethullah Gulen, a US based Islamic cleric who Ankara blames for last month's coup attempt.
Gulen denies the coup charges. Born in Turkey, he was a long-time ally of President Recep Tayyip Erdogan, but the two split in recent years. Washington says that if Turkey files an extradition request for the cleric, the US justice system would weigh its merits.
The dual moves highlight Turkey's war against the perceived followers of Gulen while it continues to squeeze Kurdish activists.
Ozgur Gundem, which publishes in the Turkish language, is focused largely on issues related to the Kurdish minority in Turkey and the conflict between the Kurdistan Workers' Party (PKK) and the state.
The court in Istanbul, according to a copy of the order circulated by activists, accused the paper of being a propaganda organ of the banned group and closed it on a temporary basis, without specifying the time frame. The order can be appealed.
The newspaper and its staff have been hounded by the authorities for more than two decades, including repeated arrests and closures.
It was relaunched under its current name in 2011, though it continued to face disruptions, as have many media outlets in Turkey. The country has the highest number of jailed reporters in Europe.
The state and the PKK restarted fighting last year after peace talks collapsed. Since then, more than 1,800 people have been killed.
Additionally, the main pro-Kurdish party in Turkey is under renewed pressure.
Peoples' Democratic Party (HDP) leader Selahattin Demirtas is facing five years in jail for allegedly supporting the PKK, though the 2013 speech cited by prosecutors was actually one in favour of the peace process between the group and the government.
The European Federation of Journalists, which records the number of media workers in jail, says 68 journalists are currently detained in Turkey.
Many were detained since the coup, but about half were taken into custody before the putsch, including Kurdish reporters working for a variety of local news outlets.
Meanwhile, Turkey also arrested Arda Akin, a journalist working with newspaper Hurriyet, the largest circulation daily, allegedly over ties to Gulen.
The arrests of alleged Gulenists since the coup, numbering upwards of 17,000 people, include businessmen, judges, prosecutors, civil servants at ministries, police and soldiers.
Turkish Prime Minister Binali Yildirim insisted alleged coup plotters will get a fair trial.
"The death penalty is a one-time death, but, there are greater deaths for them. That is an impartial and fair trial," he said, according to Anadolu.
Erdogan has repeatedly said there will be a debate in parliament over bringing back the death penalty, and if approved, he would sign it into law, amid calls from his supporters to condemn Gulen to death.
The issue could bring him directly into conflict with the European Union, as the bloc is adamantly opposed to the death penalty. Turkey is seeking to join the EU.
The president, speaking to lawyers in Ankara, said that if Europe faced a coup and repeated terror attacks it too would "bring in the death penalty," Anadolu reported.