ptpu

Note though, this would be really hard to evolve. As an analogy, the photosynthetic center RuBisCO is fairly wasteful, so any organism that can improve on RuBisCO would have a huge advantage. Only problem is RuBisCO is not easily evolvable (like brittle code), thus we don't know of any improvements although they are quite possible theoretically.

Yes, there are many ways to make isomers--it is done commonly in the pharmaceutical industry. Can be done directly via synthesis, or a racemic mix can be separated by physical processes such as crystalization or enzymatically. Most enzymes have a chirality (like the glove analogy), so they tend to create produces with a single isomer.

This said, making an organism with mixed chirality would likely not be effective because, likely, many reactions would not proceed or would proceed with poor efficiency. All D- or all L- would work fine, but any evolved organism would suffer/die with a mix of D- and L-.