Mathuki made the remarks recently when addressing virtual press conference from his offices in Arusha, Tanzania.
His comments came barely few weeks after DR Congo President Félix Tshisekedi signed the Treaty of accession by his country to the EAC. DR Congo's entry now makes EAC a seven-member bloc.
Mathuki who was briefing regional journalists on the initiatives the Secretariat put in place for DR Congo's integration, in the upcoming months, indicated that the youth in the region now have a market of about 300 million people to tap and grow their businesses.
Irrespective of the challenges that may come with an expanded community, he said, there is a huge market opportunity.
"It means markets, opportunities. It means our young people should be able, now, to take advantage of this huge market; use their talents, and see how we can exploit together. The advantages start coming along with this," Mathuki said.
"When we talk of opportunities, and investments and businesses and what it means for the youth, we are saying; if youth, with their dynamism, and their advanced digital thinking, they could take advantage and exploit this market and make sure they don't only look for jobs alone but can also now start using their skills to look for business opportunities, to see how they can exploit this market.
"I have a strong conviction that the Heads of State Summit, our Presidents in East Africa; they were largely doing this [admitting DR Congo] for the youth. They are doing this to open opportunities for the young people; meaning that you should be able now to see what you can do in DRC, if you are a youth in Tanzania, what can [youths in DRC] do in Tanzania, and come together and have a very strong vibrant community."
Benefits are there, he said, and so will be challenges but it is important to understand that the opportunities and benefits outweigh the challenges.
The potential in DR Congo includes vast arable land not being used for agriculture.
The DR Congo is expected to bolster the bloc's economic potential through various ways including opening the corridor from the Indian Ocean to the Atlantic Ocean, as well as North to South, hence expanding the economic potential of the region. Among others, the country is the world's biggest producer of cobalt, a major component in the manufacture of rechargeable batteries for electric vehicles, and Africa's main copper producer. It is a major producer of gold, diamonds, uranium, coltan, oil and other precious metals, making it one of the most resource-rich countries in the world.
Eleven percent of the goods the vast country consumes come from the six other partner states in the bloc, Mathuki said, while 35 per cent of what DR Congo consumes comes from China and other places.
Now that DR Congo is part of the EAC, Mathuki said, "We will be transforming or taking advantage of that consumption" so that whatever is produced in the region can find market in DR Congo.
The DR Congo will also, among others, be able to make better use of regional infrastructure facilities.
"They should be able to access the Dar es Salaam port and the Mombasa port. Again, they should be able to join the framework of the Common External Tariff where any goods that are produced within east Africa enjoy a tariff regime that is calculated. If you are producing your goods within east Africa, you are able to sell them within east Africa on zero per cent tariff, and so on."
The Secretariat, Mathuki said, will in the near future organize business trips to DR Congo and the other side is also planning to send business expeditions to regional countries as part of the new anticipated business interactions. Young entrepreneurs in the region are also eagerly following the news, and making plans.
Jeannette Rugero, a Rwandan tour guide and driver, told The New Times that she is now encouraged "more than before" to explore opportunities in DR Congo.
"Congo is a very beautiful country with diverse tourist attractions; national parks, culture, landscape and so much more that people want to see. The insecurity in the east is just in one part but there are many others that are secure and this is where I want to start exploring and benefiting from. The Congolese will now feel more East African and more welcome, and vice versa," she said.
From Mbeya, a region in southwestern Tanzania, Ahadi Asajile Mtweve, a broadcast journalist passionate about agribusiness, said his company which offers services including farm management, avocado seedlings, and agricultural consultancy, is excited about what he sees as a new door being opened in DR Congo.
"We deal with horticulture across East Africa," he noted, adding that, DR Congo as a new member of the EAC now "paves the way for us to open up market linkages to farm produce."
"We expect to extend our products to Congo, especially in inviting our existing clients opening up new avocado farms, professional training and agricultural consultancy to new investors from Congo," Mtweve said.
Tshisekedi's accession signature on April 8 immediately brought his country into the realms and provisions of all the protocols and regional policies of the bloc.
Mathuki said: "They are normally given a period of six months. But therefore it means you can do it in a week, two weeks, one month, two months, or within that period, depending on the structures or the systems that you have in your own country."
After signing the Treaty of accession, the new member now has up to September 29 to undertake internal and constitutional processes to ratify the EAC Treaty and submit to the EAC Secretary General, and subsequently join all programmes and activities of the bloc.