Hi shantanu, 

I think the simple protocol would be to determine the biomass in terms of chlorophyll and carotenoids contents of Chlorella vulgaris. These pigments can easily be extracted with DMSO, methanol or 85% acetone and estimated their content based on standard formulas.

Alternatively, if sodium citrate solution only dissolves alginate beads,  and then you may separate the algae biomass by centrifugation, and then the pellets can be used to obtain both fresh weight biomass, oven-dried or freeze-dried dried biomass data.

Hope this helps.