The phrase "a portion that is" is correct and usable in written English.
It can be used when referring to a specific part or segment of something, often in a descriptive or explanatory context.
Example: "The report includes a portion that is dedicated to analyzing the financial trends of the past year."
Alternatives: "a segment that is" or "a part that is".
In contrast however, 4.92% of the A. arilaitensis chromosome is composed of ISs elements, a portion that is at least 15 fold higher than for the other Arthrobacter strains.
"Every time we have had a change, there is a portion that is viable and helpful," she said.
Domestic discretionary programs account for about 15 percent of the annual budget, a portion that is not growing.
Sampling is the removal from a given lot of material a portion that is representative of the whole yet of convenient size for analysis.
On average, we found that a portion that is doubled in size is judged to be only 72% larger than the original size, whereas one that is halved appears to be 53% of the original size.
This is the idea that there is a portion of the team that is managing traditional IT responsibilities and a portion that is working more on the art of the possible which is more forward-looking and innovative.
"There's a portion that are never tested," she said.
The aid was divided among the locals and each man got a portion that was enough for two days.
We were completely happy with our loose, creamy mushroom risotto, served in a portion that was sufficient but not elephantine (the same could be said about most Sage serving portions).
"Every child's appetite is different so portion sizes aren't set nationally - but cooks do get to know their pupils, and should make sure they are getting a portion that's approriate for them".
It was served in a portion that was almost entrée sized and included a small side of very good garlic broccolini and two little squares of potato gratin.
