A novel two-phase bioreactor for microbial hexavalent chromium removal from wastewater.

Α novel two-phase bioreactor for the microbial removal of Cr(VI) from wastewater with high chromium concentration (up to 1350ppm) is developed. Among several potential solid-phase adsorbents tested, Cloisite® 30B, a natural montmorillonite modified with a quaternary ammonium salt that absorbs Cr(VI) in a reversible manner proved to be optimal as the solid phase of the bioreactor. Cloisite® 30B has no toxicity to the acclimated biomass and keeps the concentration of Cr(VI) ions at sub-inhibitory levels that ensure the efficient microbial removal of Cr(VI). The microbial removal of Cr(VI) was achieved using an acclimated mixed culture developed from anaerobic sludge. The novel bioreactor was operated as a Sequencing Batch Reactor (SBR) under anaerobic and mesophilic conditions for over 200 cycles, without further addition of the solid adsorbent, and led to even 100% removal of Cr(VI) with high removal rates for concentrations ranging from 900-1350mg/L Cr(VI). The reduction of Cr(VI) to the less toxic Cr(III) was proved to be mediated by lactate, generated by a lactic acid bacterium, 99% similar to Pediococcus acidilactici as demonstrated by molecular methods The reduction of Cr(VI) took place extracellularly where it reacts with the lactic acid produced during the process of glycolysis.

Prediction of the soluble myoglobin content of cooked burgers.

The time-temperature profiles for cooking in-house made beef and lamb burgers were determined using a thermocouple placed in the centre of the burger. From these data the soluble myoglobin remaining in the burger was predicted using kinetic data from previously reported model experiments. First order kinetics were assumed for the denaturation of the myoglobin. A good correlation between observed and predicted data was observed. Thus the "degree of doneness"of different meats can be predicted when cooked under specified conditions.

Effect of muscle type, salt and pH on cooked meat haemoprotein formation in lamb and beef.

The rate of cooked meat haemoprotein formation, measured as the rate of loss of myoglobin solubility, in lamb was dependent on the muscles anatomical location and temperature. Lamb longissimus dorsi musle at 55 to 70°C formed cooked meat haemoprotein more rapidly than the muscles in the shoulder and leg. The formation in lamb was more rapid than in beef. The rate in high pH beef (7.25) l. dorsi was lower than found in beef l. dorsi of normal pH but in low pH lamb (5.38) l. dorsi the rate was, at most temperatures, also slower than found in this muscle from lamb of normal pH. In the presence of NaCl the rate of cooked meat haemoprotein formation was faster (almost doubled at 2g/100g meat) than found in the corresponding salt free lamb and beef samples. Other additives commonly added to meat products (mechanically recovered meat, oil, polyphosphates, soya, whey and caseinate) had little effect on the rate of cooked meat haemoprotein formation, at the levels normally used in meat products. It is concluded that for lamb products little if any myoglobin will remain soluble, and the products will look cooked before the recommended thermal treatment to inactivate Escherichia coli O157:H7 has been achieved. ©