Houston founder shares how he's using tech to make digital media more effective and equitable

houston innovators podcast episode 173

This month, Mark Walker is celebrating his company's one year anniversary of going public — only the ninth Black-founded business to accomplish this feat on a U.S. stock exchange. Photo courtesy

After working in both sides of the advertising world, Mark Walker thought he could reimagine a platform that would be more efficient and equitable.

Walker co-founded his company, Direct Digital Holdings, an adtech platform, after serving in several roles — from an early hire at Houston digital media startup Questia to business development director at NRG Energy and COO of EBONY Media. He shares on the Houston Innovators Platform how he took this experience in tech, advertising, and media to create his company's platform.

"NRG Energy gave me a top-down view of the value chain, and Ebony gave me a bottoms-up view of the value chain of how media is purchased," Walker says on the show. "At Direct Digital Holdings, we help companies buy and sell media — and we leverage technology to do it. It's really the culmination of both of those experiences."

With over 30,000 publishers on its platform, Direct Digital makes it easier for its core customers — middle market companies looking to buy into the digital media ecosystem — to tap into these opportunities without the tech know-how they might otherwise need. Walker explains that at EBONY, he saw how small to midsize publications — especially the multicultural ones — were being left out on the ad selling side of the equation. The Direct Digital platform bridges the gap on each end.

Founded in 2018 in partnership with Keith Smith, who went through similar professional experiences, Direct Digital went public exactly one year ago after growing the company through strategic M&A activity. Walker says the decision to IPO made the most sense for his company — though it wasn't an easy process. Direct Digital is only the ninth company founded by a Black entrepreneur to go public on a US stock exchange.

"If you think the process is hard — it actually is," Walker says on the journey to IPO. "We were a privately held company, and we knew we had a good growth trajectory and we looked a couple different options. We decided to go public in a very traditional way."

Walker explains there were some risks involved, but the co-founders ultimately decided to shy away from adding in investors who might not have the same ideas for the company's future.

Direct Digital has been a Houston company from the star — despite the city not being home to a booming adtech ecosystem. Instead, Houston — with its collection of Fortune 500 companies and rich diversity — has allowed the business to stand out.

"If you look at and reflect on how our company has been built — from our board of directors to our leadership and management team — we're a majority minority organization all the way across the board," Walker says. "Diversity is very important to us. It's the lifeblood of our business — especially because we're serving publishers in those communities in big way. And moreso, we think you get the best product, thoughts, and ideas from a diverse workforce, and Houston fits right into that mold for us."

Walker shares more about his company's future, advice on IPO, and what all he's watching in adtech — from AI to streaming — on the podcast. Listen to the interview below — or wherever you stream your podcasts — and subscribe for weekly episodes.


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Pioneering Houston biotech startup expands to Brazil for next phase

On the Move

Houston biotech company Cemvita has expanded into Brazil. The company officially established a new subsidiary in the country under the same name.

According to an announcement made earlier this month, the expansion aims to capitalize on Brazil’s progressive regulatory framework, including Brazil’s Fuel of the Future Law, which was enacted in 2024. The company said the expansion also aims to coincide with the 2025 COP30, the UN’s climate change conference, which will be hosted in Brazil in November.

Cemvita utilizes synthetic biology to transform carbon emissions into valuable bio-based chemicals.

“For decades Brazil has pioneered the bioeconomy, and now the time has come to create the future of the circular bioeconomy,” Moji Karimi, CEO of Cemvita, said in a news release. “Our vision is to combine the innovation Cemvita is known for with Brazil’s expertise and resources to create an ecosystem where waste becomes opportunity and sustainability drives growth. By joining forces with Brazilian partners, Cemvita aims to build on Brazil’s storied history in the bioeconomy while laying the groundwork for a circular and sustainable future.”

The Fuel of the Future Law mandates an increase in the biodiesel content of diesel fuel, starting from 15 percent in March and increasing to 20 percent by 2030. It also requires the adoption of Sustainable Aviation Fuel (SAF) and for domestic flights to reduce greenhouse gas emissions by 1 percent starting in 2027, growing to 10 percent reduction by 2037.

Cemvita agreed to a 20-year contract that specified it would supply up to 50 million gallons of SAF annually to United Airlines in 2023.

"This is all made possible by our innovative technology, which transforms carbon waste into value,” Marcio Da Silva, VP of Innovation, said in a news release. “Unlike traditional methods, it requires neither a large land footprint nor clean freshwater, ensuring minimal environmental impact. At the same time, it produces high-value green chemicals—such as sustainable oils and biofuels—without competing with the critical resources needed for food production."

In 2024, Cemvita became capable of generating 500 barrels per day of sustainable oil from carbon waste at its first commercial plant. As a result, Cemvita quadrupled output at its Houston plant. The company had originally planned to reach this milestone in 2029.

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This story originally appeared on our sister site, EnergyCapitalHTX.

Houston Public Library to open new state-of-the-art TECHLink center in 2025

Innovation Station

Work is underway for a new state-of-the-art TECHLink space from Houston Public Library (HPL). The free center for innovators and creatives is expected to open in fall 2025 at Vinson Neighborhood Library this year.

The new 3,480-square-foot space will replace the branch’s existing HPL Express area, which closed January 25 in preparation for construction. This will be HPL's fifth TECHLink center, and it will serve one of South Houston's busiest libraries, notes a release.

“I always look forward to seeing our customers’ creative wheels turning and formulating plans once they recognize all of the technologies and equipment that they can freely access,” Roland Lemonius, TECHLink Division Manager, said in a news release.

TECHLink Vinson will include HPL's largest TECHLink video studio and also a dedicated studio/set for podcasts and vloggers.

HPL TECHLinkVideo studio at TECHLink Dixon. Courtesy of HPL

It will also feature a music recording studio, an editing lab, and a Makerspace lab for 3D printing and laser engraving. Virtual and in-person training opportunities will be available in a training lab in the future, according to HPL.

For kids, the Tiny Techs Zone offers a dedicated area to educate youth on 3D printing and robotics.

“Being able to enhance their quality of life in this way along with our other library services is very rewarding,” Lemonius added in the release.

TECHLink Vinson will join four other locations:

  • TECHLink Alief
  • TECHLink Dixon
  • TECHLink Scenic Woods
  • TECHLink Walker
Find a virtual tour of the Dixon location here.


croployaltyshopping_cartlocal_librarydeleteTECHLINKTECHLink Vinson will join four other locations, including DIxon. Courtesy of HPL


Texas universities develop innovative open-source platform for cell analysis

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What do labs do when faced with large amounts of imaging data? Powerful cloud computing systems have long been the answer to that question, but a new riposte comes from SPACe.

That’s the name of a new open-source image analysis platform designed by researchers at Baylor College of Medicine, Texas A&M University and the University of Houston.

SPACe, or Swift Phenotypic Analysis of Cells, was created to be used on standard computers that even small labs can access, meaning cellular analysis using images produced through cell painting has a lower barrier to entry than ever before.

“The pharmaceutical industry has been accustomed to simplifying complex data into single metrics. This platform allows us to shift away from that approach and instead capture the full diversity of cellular responses, providing richer, more informative data that can reveal new avenues for drug development,” Michael Mancini, professor of molecular and cellular biology and director of the Gulf Coast Consortium Center for Advanced Microscopy and Image Informatics co-located at Baylor College of Medicine and TAMU Institute for Bioscience and Technology.

SPACe is not only accessible because of its less substantial computational needs. Because the platform is open-source, it’s available to anyone who needs it. And it can be used by academic and pharmaceutical researchers alike.

“The platform allows for the identification of non-toxic effects of drugs, such as alterations in cell shape or effects on specific organelles, which are often overlooked by traditional assays that focus largely on cell viability,” says Fabio Stossi, currently a senior scientist with St. Jude Children’s Research Hospital, the lead author who was at Baylor during the development of SPACe.

The platform is a better means than ever of analyzing thousands of individual cells through automated imaging platforms, thereby better capturing the variability of biological processes. Through that, SPACe allows scientists an enhanced understanding of the interactions between drugs and cells, and does it on standard computers, translating to scientists performing large-scale drug screenings with greater ease.

"This tool could be a game-changer in how we understand cellular biology and discover new drugs. By capturing the full complexity of cellular responses, we are opening new doors for drug discovery that go beyond toxicity,” says Stossi.

And the fact that it’s open-source allows scientists to access SPACe for free right now. Researchers interested in using the platform can access it through Github at github.com/dlabate/SPACe. This early version could already make waves in research, but the team also plans to continually improve their product with the help of collaborations with other institutions.

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