I recently brewed a 30L batch of beer using only half a packet of dried yeast. The instructions told me to use the full packet. The beer came out enjoyable, it wasn't a bad batch or anything, it was just lacking some of the fruitiness associated with that strain of yeast. I definitely had better results in the past. I realized I had underpitched this my yeast. But my question is can I still harvest the yeast and use it to make a starter for my next batch?