#Hashtags and @ are usable in the Twitter bio.
Hashtags are important for searchability on Twitter. Not having hashtags in your bio will hinder it. Hashtags are not the only things that can be used in the bio; @… can be used also. This good for linking your business with your personal accounts. I have added my personal to @beyondtdaymedia and vice versa because I want my followers to know who I am. Do not forget that links can be added too. Not only can you have your main link, probably to your website, you can have as many links in the 160 character limit, 20 more than a regular tweet, as you want. Remember do not abuse the #hashtag twitter will punish you for it.