μmax = 0.01 h-1 0.05 h-1 fPHB = 0.15 0.3 0.7 0.15 0.3 0.7 quotient є n = 1 1.00 0.99 0.94 0.98 0.94 0.68 n = 2 0.99 0.98 0.87 0.95 0.88 0.35 n = 5 0.98 0.94 0.68 0.88 0.70 excess1 Minimum substrate concentration Smin (mM) n = 1 no growth no growth 0.69 0.32 0.24 0.06 n = 2 no growth 279.1 0.62 0.31 0.22 0.03 n = 5 no growth 24.1 0.42 0.28 0.17 excess1

Table 1: Values for the relative maintenance reduction, expressed as quotient є, and the minimum substrate concentration Smin at μmax = 0.01 and 0.05 h-1 for various PHB fractions and coupling factors n. Calculations according to equations 16 to 22 were made assuming S = 1 mM, η = 2, YmaxactBM = 0.789 g active biomass (g MTBE)-1, mS = 0.21 mmol MTBE g-1 h-1, and KS = 1 mM. 1)Excess means that more energy is made available from PHB synthesis than needed for biomass synthesis which formally results in a net-production of energy.