Assertion: Vitamin B2 is found in cereals, green vegetables, brewer"s yeast, egg white, milk and liver.
Reason: It can be commercially produced by some yeasts.

Both Assertion (A) and Reason (R) are correct but R is not the correct explanation of A.

Vitamin B2, also known as riboflavin, is found in various food sources, including cereals, green vegetables, brewer's yeast, egg white, milk, and liver.

Cereals such as wheat, rice, and oats can contain significant amounts of vitamin B2. Green vegetables like spinach, broccoli, and asparagus are also good sources of this vitamin. Brewer's yeast, which is commonly used in brewing beer and baking, is another natural source of riboflavin. Additionally, egg white, milk, and liver are known to contain vitamin B2 in varying amounts.

Furthermore, the reason provided is also accurate. Vitamin B2 can be commercially produced by some yeasts through a fermentation process. Certain strains of yeast, such as Ashbya gossypii, are capable of synthesizing riboflavin, and they are cultivated on an industrial scale to produce this vitamin. The yeast is grown in a nutrient-rich medium, and during fermentation, it produces riboflavin, which can be extracted and used for various applications, including food fortification and vitamin supplements.

In conclusion, the assertion that vitamin B2 is found in cereals, green vegetables, brewer's yeast, egg white, milk, and liver is correct. Additionally, the reason provided, stating that it can be commercially produced by some yeasts, is accurate.