A microorganism is grown in a batch culture using glucose as a carbon source. The apparent growth yield is $0.5 \frac{\text{g biomass}}{\text{g substrate}}.$ The initial concentrations of biomass and substrate are $2 \; \text{g L}^{-1}$ and $200 \; \text{g L}^{-1},$ respectively. Assuming that there is no endogenous metabolism, the maximum biomass concentration that can be achieved is _________ $ \text{g L}^{-1}.$