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The partial recovery of sodium as NaOH and sodium-free aliphatic carboxylic acids (formic and acetic acids together with various hydroxy carboxylic acids) from alkaline hardwood black liquor (BL, pH about 14) was studied by using electrodialysis (ED). In the first phase, the lignin was partly (about 59% of the initial lignin) precipitated from BL by carbonation (pH to 8.5). Furthermore, the carbonated liquor, mainly containing NaHCO3/Na2CO3 and Na salts of aliphatic carboxylic acids and lignin, was subjected to ED for recovering NaOH and sodium-free aliphatic acids. In the second phase, the carbonated BL was further acidified with H2SO4 (pH to about 2.5) for precipitating more lignin (about 90% of the initial lignin) with the simultaneous liberation of aliphatic acids. The Na2SO4 that was formed was then separated from the acidified liquor by precipitation with methanol and treated by ED to produce NaOH and H2SO4. For ED experiments, a batch laboratory-scale apparatus containing cation selective and bipolar membranes was used at 20 V. Within an ED treatment time of 5 h the recovery rate of sodium from carbonated BL, model Na2SO4, and precipitated Na2SO4 was 0.044, 0.110, and 0.104 mol Na/h, corresponding to an energy consumption of 1.76, 0.38, and 0.43 kWh/mol Na, respectively. In each case, the total amount of sodium recovered was about 90%.

BACKGROUND: A thermophilic lipase-producing Geobacillus thermodenitrificans strain AV-5 was isolated from the Mushroom Spring of Yellowstone National Park in WY, USA and studied as a source of lipase for transesterification of vegetable oils to biodiesel. RESULTS:A maximum activity of 330 U mL −1 was produced on 2% (v/v) waste cooking oil at 50 ∘ C, pH 8, aeration rate of 1 vvm and agitation speed of 400 rpm. However, the higher lipase productivity (14.04 U mL −1 h −1 ) was found at a volumetric oxygen transfer coefficient (k L a) value of 18.48 h −1 . The partially purified lipase had a molecular weight, temperature and pH optimum of 50 kDa, 65 ∘ C and pH 9, respectively, and was thermo-alkali stable: at 70 ∘ C, it retained 81% activity and 45% stability; at pH 10 it lost only 15% and 2.6% of its maximum activity and stability, respectively. Enzyme kinetic studies with p-nitrophenyl laurate as substrate revealed high substrate specificity (k m of 0.440 mmol L −1 ) and kinetic activity (v max of 556 nmol mL min −1 ) of lipase. CONCLUSIONS: The k L a was found to be highly dependent on aeration and agitation rates. Following optimization of fermentation medium and parameters, a 7.5-fold increase in lipase production by G. thermodenitrificans was attained. The lipase activity and substrate specificity (as k m ) are among the highest reported in the literature for bacterial lipases. It was demonstrated that the enzyme can produce biodiesel from waste cooking oil with a conversion yields of 76%. Fermentation studies on lipase productionEffect of temperature and pH on lipase production Bacterial lipases are greatly influenced by physical fermentation parameters such as temperature and pH. Most thermophilic aerobic geobacilli have optimal growth and enzyme production in

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