Biomedical subjects

C M Cuevas

Publications and source records attributed to C M Cuevas.

4 recordsLinked to original sources

PubMed2006

Stability and activity of anaerobic sludge from UASB reactors treating sewage in subtropical regions.

The production of small amounts of well-stabilized biological sludge is one of the main advantages of upflow anaerobic sludge bed (UASB) reactors over aerobic wastewater treatment systems. In this work, sludge produced in three pilot-scale UASB reactors used to treat sewage under subtropical conditions was assessed for both stability and specific methanogenic activity. Stability of primary sludge from settling tanks and digested sludge from conventional sludge digesters was also measured for comparison purposes. Kinetic parameters like the hydrolysis rate constant and the decay rate constant were calculated. High stability was observed in sludge from UASB reactors. Methanogenic activity in anaerobic sludges was relatively low, probably due to the low organic matter concentration in influent sewage. Knowledge on sludge growth rate, stability, and activity might be very useful to optimize sludge management activities in full-scale UASB reactors.

Anaerobiosis↗

PubMed2002

Removal efficiency and methanogenic activity profiles in a pilot-scale UASB reactor treating settled sewage at moderate temperatures.

The performance of a sewage treatment system consisting of a settler followed by an Upflow Anaerobic Sludge Bed (UASB) reactor is described. Mean ambient and sewage temperature were 16.5 and 21.6 degrees C, respectively. Total Chemical Oxygen Demand (CODt) concentration averaged 224.2 and 152.6 mg/L, for raw and settled sewage, respectively. The effluent concentration was 68.5 mgCODt/L. Total and suspended COD removal efficiencies of approximately 70 and 80%, respectively, have been observed in the system at a mean Hydraulic Retention Time (HRT) of 2 + 5 h. Maximum COD removal efficiency was achieved in the UASB reactor when upflow velocity (Vup) was 0.43 m/h (HRT = 6 h). Mean Specific Methanogenic Activity (SMA) and Volatile Suspended Solids (VSS) concentration in the granular sludge bed were 0.11 gCOD-CH4/gVSS.d and 30.0 gVSS/Lsludge, respectively. SMA was inversely related to VSS concentration, and both parameters varied along the sludge bed height. The Solids Retention Time (SRT) in the reactor was 450 days. Sludge characteristics have not been affected by changes of up to one month in Vup in the range 0.28-0.85 m/h (HRT 3-9 h). This system or two UASB reactors in series could be an alternative for sewage treatment under moderate temperature conditions.

Bacteria, Anaerobic↗

PubMed1998

[Lipoxygenase and trypsin inhibitor inactivation in soymilk processing by direct milling and ultra high temperature (DM-UHT)].

Soymilk production by a new process based on Direct Milling of soy grits and Ultra High Temperature (DM-UHT) has been studied at laboratory scale in order to evaluate solids and protein extraction, lipoxygenases (LO) and Trypsin Inhibitors (TI) inactivation during milling and heat-treatment steps. For TI measurements in soy extracts and soymilk a modification of the classical Kakade method (17) was used. Highest extraction yields were accomplished at 70 degrees C and 2 minutes milling of soy grits. LO was appreciably inactivated when using, as dispersing medium for milling, 0.01M sodium carbonate (Residual Activity 14%) instead of water (Residual Activity 46%), so in this way lower levels of undesired substances can be generated. LO destruction in the resulting suspension was finished by a short heating (30 seconds) from 70 degrees C to boiling temperature (96 degrees C). On the other hand, TI were not fully inactivated in milling nor even in the steaming step at 96 degrees C for many minutes. The TI were inactivated to the accepted levels for soymilk in the final UHT step at 135 degrees C and 2 minutes, being possible at the same time to carry out the simultaneous microorganisms destruction.

Food Handling↗

PubMedDate not supplied

[Alkaline protease production].

The influence of culture medium composition on alkaline protease production was studies. Various carbon sources such as glycerol, glucose, lactose and starch were tested. Different concentrations of lactose and bactopeptone have been tested. The optimum medium composition was found to be: (g/l) lactose 20.0; bactopeptne Difco 10.0; NaCl 1.5;mgSO47.H20 0.15; CaCl2 0.06; K2HPO4 1.5; KH2PO4 1.5; Na2SO4 1.5; MnCL2.4H2O 0.01. A cell concentration of c.a 9.5 g/l has been obtained after 30 hours. The maximun alkaline protease production (5,000 uAPAM/ml) was attained after 60 hours. The trials were carried on rotary shaker in 1 liter erlenmeyer flasks containing 250 ml of medium.

Bacillus subtilis↗