초록
<P><B>Abstract</B></P> <P>In this work the thin film composite nanofiltration (TFC-NF) membrane was fabricated for lactic acid separation in membrane bioreactor. The morphological study was carried out with scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM studies indicated that using interfacial polymerization causes a rough and dense film to be formed on the polyethersulfone (PES) support membrane. The permeate flux and separation properties of the membrane was investigated at 25 °C and trans membrane pressure (TMP) of 5 bar and was compared with 3 commercial NF membranes. The high lactose and low lactic acid rejection of 80% and 19% was obtained with TFC NF membrane. The membrane was used to produce lactic acid from whey lactose in membrane bioreactor (MBR). Continuous lactic acid production has two stages of Integration of fermentation and membrane separation which were assessed and compared to the conventional bioreactor performance (CBR). In order to produce lactic acid from whey, the <I>Lactobacillus bulgaricus</I> (ATCC 8001) was used in the process. The maximal productivity of 6.1 gL<SUP>−1</SUP> h<SUP>−1</SUP> was obtained at the dilution rate of 0.24 h<SUP>−1</SUP>, while the value obtained in the CBR was 3.4 gL<SUP>−1</SUP> h<SUP>−1</SUP> at the same dilution rate. The maximum concentration of lactic acid was obtained at the dilution rate of 0.04 h<SUP>−1</SUP> in both MBR and CBR with values of 38.2 and 22.5 gL<SUP>−1</SUP>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The TFC-NF membrane was synthesized and evaluated for LA production process. </LI> <LI> Performance of the four types of membranes was investigated. </LI> <LI> High lactic acid concentration (123 g/L) and productivity (17.1 g/L/h) was obtained. </LI> <LI> The critical lactose concentration in MBR which the cell growth hampered was 150 g/L. </LI> </UL> </P>