100km each way 5days a week is a huge time commitment.
So, maybe you could commute by bike one day a week, perhaps Friday, and car commute the rest of the week.
I dare say, the mileage you would do on that day is much greater than the mileage you are doing on the bike for the entire week now. So your fitness level does not decrease.
And it's only for a year.
Something to think about.