Yes, PROBIOTIC is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, O 1, B 3, I 1, O 1, T 1, I 1, C 3.

Is it a valid word?

PROBIOTIC is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a beneficial bacterium found in the intestinal tract of healthy mammals; often considered to be a plant

Also: probiotic bacterium, probiotic microflora, probiotic flora.