Carbohydrates, the most abundant biomolecules on earth, are produced by:

Some photosynthetic bacteria such as Rhodopseudomonas can prepare carbohydrates. But during this type of food synthesis $\mathrm{O}_2$ does not evolved because in this case hydrogen donor is other than $\mathrm{H}_2 \mathrm{O}$. Algae (green and blue green) and all green plant cells prepare their food (carbohydrate) through photosynthesis. Here, hydrogen ions are donated by water molecules by the process of photolysis of water i.e., $\mathrm{O}_2$ is released during this type of food synthesis.