Now I am ending my PhD in chemistry but love to switch to research in biology (bioinformatics or biochemistry). I already have wide knowledge in biology via university courses and latter learning with MOOCs, as well as programming. Please give a hint on getting a job in biology.
The difference between chemistry and biology is not so great that it's tremendously difficult to transition between the two. (Versus, say, transitioning from a historian of first century Mesopotamia into quantum physics.)
If you're looking for a postdoc, then I'd suggest looking for a lab that's doing the same sort of thing you want to be doing in the end, then figure out how your current skill set could potentially be applied toward that problem. For example, if you're an organometallic chemist and want to move into biochemistry, look for labs who are working on metalloenzymes, or with protein structure determination using paramagnetic metal ions.
Chances are, there's someone out there who is working at the intersection of your current expertise and your desired expertise. Get a postdoc position with them. At first you'll be "the chemistry guy", called upon to be the expert on you Ph.D. topic. But over time you'll pick up more and more of the biology, and can transition into more straight-biology research. Once you leave your postdoc, you'll have the biology experience (and publications) under your belt, and will be able to demonstrate competence to people interviewing you.
One caveat with this is that - like all postdoc interviews - you need to feel your advisor out on your plans. Many will be fine with your transitioning from one topic to the other, but there will be a few who will want to rigidly slot you into your Ph.D. role, making you a chemistry mercenary for your lab. Obviously, don't take a postdoc with those sorts of people.
If you're talking about a "real job", then things get slightly more complicated. A postdoc is technically a training position, and so broadening your horizons is expected and desired. For "real jobs", though, people are typically hired to do a particular role, and they're expected to be mostly accomplished for that role. That's not to say that roles don't change over time. A similar approach to the postdoc can also be used here. Find a company which is primarily a biology company, but needs your chemistry expertise. At first you'll be doing just the chemistry work, but over time you may be able to pick up more involvement with the biology side of things.
One type of place I might recommend you try for is a startup. The environment in a startup company is constantly changing, so people who work there typically need to be flexible and do many jobs. If you get hired at a mostly-biology startup, you might be brought on as a chemist, but it's likely that you'll be called upon to pick up biology as the job requirements change.
Again, feeling the company out in the interview is key. Ask how they see the position changing over the next 2/5/10 years. Do they seem receptive to you picking up a biology role, or do they want you to rigidly slot into a chemistry-only slot?
Regarding picking up another degree, I personally don't think it's worthwhile for two subjects as close as Chemistry and Biochemistry/Bioinformatics. A big part of a Ph.D. is training on how to do research, and there's not that much difference between how research is done in Chemistry and Biochemistry. If you have a Ph.D. in Chemistry, you should be competent enough to pick up biology research on your own. If you're interested in having a dual Ph.D., by all means go for it, but if you're just interested in doing more biology-focused research, learning it in a non-degree setting is probably better.
If you already know biology well enough, getting a job in biology may very well be possible for a chemistry graduate. I was an electrical engineering graduate with specialization in micro and nanotechnology. However, all of my real jobs outside the university have been mostly about computer science and communications engineering, and now I have started a PhD in communications engineering.
The key is to know the field you are applying for a job in. The knowledge may have been obtained from university courses, or alternatively through self-studying. In my case, I'm an expert self-studied computer programmer which helped me a lot. The recruiters mostly don't care: deep interest in and knowledge of the field is always seen as a merit. They'll obviously test your knowledge, but if you pass those tests, things are going well for you.
I understand that you are applying for a job in academia, not for a job in the private sector. This may be somewhat harder than for my case, as academia requires deeper knowledge of the subject than typical private sector jobs. But if I was able to do the transition in a way that allowed me to start my PhD, I suspect it may be possible after finishing the PhD. Another option would be to do another PhD. If you work in academia, you will eventually have to start publishing, and enough many publications related to each other practically means that you have your second PhD ready.