During exponential growth: $x = x_0 \cdot 2^{n}$ where $n$ is the number of doublings. In 8 hours with a doubling time $t_d = 2$ h: $n = 8/2 = 4$ doublings. Therefore: $x = 0.1 \times 2^4 = 0.1 \times 16 = \mathbf{1.6}$ g/L. Equivalently, using $\mu = \ln2/t_d = 0.347$ h⁻¹: $x = 0.1 \cdot e^{0.347 \times 8} = 1.6$ g/L.