61 0.34 8.82 0.15 0.83 Sucrose 1.51 0.46 13.10 0.13 0.68 Lactose 1.35 0.24 8.00 0.15 0.89 Trehalose 1.50 0.43 9.21 0.12 0.74 Fructose 1.51 0.34 7.50 0.18 0.78 Dextrins 1.61 0.31 11.0 n.d. n.d. The concentration AZD1080 research buy of biomass and selleck kinase inhibitor lactic acid were measured in the broth after 24 h of growth. Yx/s indicates g of dry biomass produced per g of substrate; Yp/s indicates g of lactic acid produced per g of substrate; μ8h indicates the specific growth rate in h−1 calculated in the first

8 h of growth. Values are an average of 3 different experiments with standard deviations ≤ 5%. Batch and microfiltration fermentation processes Glucose and sucrose were selected as carbon sources for the following batch experiments. During these experiments L. crispatus L1 demonstrated a similar growth rate and final concentration of cells. The maximum titer of biomass on the two substrates was slightly different, in particular, 3.9 ± 0.2 gcdw∙l−1 were obtained on glucose and 3.4 ± 0.1 gcdw∙l−1 on sucrose eFT508 (Table 2). The final amount of lactic acid was also quite similar, and it corresponded to 12 and 14 g∙l−1 on glucose and sucrose, respectively. Product (lactate) inhibition was also studied to better characterize the physiology of L. crispatus L1. Increasing amounts of sodium lactate added to the SDM medium at a fixed pH lowered the initial specific growth rate (1–3 h). In particular, μ appeared to

be reduced by half with 45 g∙l−1 lactate (Figure 2). In order to dilute lactic acid and overcome inhibition Arachidonate 15-lipoxygenase problems, a bioreactor with microfiltration modules was used to perform in situ product removal experiments (Figure 3). A maximum of 27.1 gcdw∙l−1 in 45 h of growth were produced with a final

concentration of 46 g∙l−1 of lactic acid. As it is shown in Table 3, a 7-fold improvement of the final titer of biomass was achieved by microfiltration experiments compared to previous batch processes. Moreover the total amount of lactic acid produced was equal to 148 g (ϕ = 0.37 g∙l−1∙h−1) with a Yp/s of 0.75 g∙g−1 (Table 3). All results presented are average of at least 3 experiments. Table 2 Yield of biomass and lactic acid obtained in batch experiments of L. crispatus L1 grown on SDM supplemented with 20 g · l −1 glucose or sucrose as main carbon sources Carbon source Cell dry weight (g · l−1) Lactic acid (g · l−1) μmax(h−1) Glucose 3.8 ± 0.3 11.5 ± 0.5 0.84 Sucrose 3.3 ± 0.2 13.6 ± 0.4 0.60 The medium contained soy peptone and yeast extract as nitrogen sources. Figure 2 Lactate inhibition curve. The graph shows the specific growth rate of L. crispatus L1 using increasing concentrations of sodium lactate in the medium at pH 6.5. Figure 3 Growth of L. crispatus L1 in a microfiltration experiment. Time course of biomass, production of lactic acid and residual glucose on SDM.