it’s already hitting the shelves. it’s used as a feedstock for multiple animal farms (mostly fish), and it’s also used as a dietary supplement for human consumption in the US. Source

Although i gotta admit, it has its issues. It is frequently contaminated with traces of toxins, which makes it a bit hazardous. It would need genetic engineering IMO before it can be used at larger scales. But the idea is there, and it’s actively researched by a lot of parties, including space agencies.