ABSTRACT
In SBR reactor, the mature granular sludge fed with sodium acetate was gradually cultivated with different carbon sources (sodium acetate/glucose ratio was 1:0, 3:1, 1:1, 1:3 and 0:1, in terms of COD, respectively). During the five stages, the physical, biochemical properties, extracellular polymeric substances (EPS), phosphorus fractions and nitrogen and phosphorus removal efficiency of granular sludge were studied. 705 days' experimental results were showed as follows. At stage â £, the granular sludge had the smallest diameter of 0.5 mm; moreover the phosphorus release/uptake rate, denitrification rate and the total phosphorus (TP) content were the lowest. While at stages â and â ¡, the phosphorus release/uptake and denitrification rates were the highest, meanwhile, the TP content reached up to 72.36 mg·g-1, and the EPS content was about 350 mg·g-1, as a result, the nitrogen and phosphorus removal efficiencies were both over 94%. Nevertheless at stage â ¤, the biochemical rates were slightly slower than values of stages â and â ¡, simultaneously the TP, glycogen and EPS contents in sludge were maintained at 69.60 mg·g-1, 224.18 mg·g-1 and 200 mg·g-1, respectively, while high nitrogen and phosphorus removal efficiency was obtained. During all stages, Ca-P was the main phosphorus fraction, and inorganic phosphorus(IP) was closely related to phosphorus removal of granular sludge.
Subject(s)
Carbon/chemistry , Nitrogen/isolation & purification , Phosphorus/isolation & purification , Sewage/chemistry , Waste Disposal, Fluid , Bioreactors , Denitrification , Glycogen/chemistryABSTRACT
The cDNAs encoding four major phospholipases A2 (PLA2s) were sequenced while the expressed sequence tags of Gloydius intermedius venom glands were constructed. These PLA2s were designated as Gintexin-A precursor, Gintexin-B, Gin-E6a and Gin-E6b, respectively. The deduced amino acid sequences of the former two PLA2s are 80% and 90% identical to those of crotoxin-A-precursor and crotoxin-B1, respectively. We also purified Gintexin-A, Gintexin-B, Gin-E6a and Gin-E6b like PLA2 from the venom. The latter three PLA2s are enzymatically active but not strongly anticoagulant for human plasma. Gin-E6a and E6b-like PLA2s induced mouse platelet aggregation but inhibited rabbit platelet aggregation. The isolated Gintexin, a 1:1 complex of Gintexin-A and Gintexin-B, blocked the twitch of chick biventer cervicis tissue presynaptically. Results of N-terminal sequencing and peptide mass fingerprinting reveal that Gintexin-A undergoes proteolytic processing similar to crotoxin-A. This is the first time heterodimeric ß-neurotoxins are found in Asian pitviper venom, and incompatible neurotoxic- and hemorrhagic-type venoms are found to evolve in parallel within the genus Gloydius, like in Crotalus. Thus, G. intermedius probably is the ancestor of rattlesnakes with type-II venom, and characterization of its venomics helps us to understand the evolution of heterodimeric neurotoxic PLA2s and the paedomorphic trend observed in Neotropical rattlesnake venoms. BIOLOGICAL SIGNIFICANCE: For the first time, a heterodimeric neurotoxic PLA2 (designated as Gintexin) has been isolated from the venom of an Asian pitviper, which shows a characteristic venom gland transcriptome similar to those of the neurotoxic type rattlesnakes. The fact that the venom of G. intermedius is less hemorrhagic than those of other Gloydius species, reveals that incompatible neurotoxic- and hemorrhagic-type venoms have evolved in parallel within the genus Gloydius, like the genus Crotalus. Our findings suggest that G. intermedius is the most probable ancestor of some Neotropical rattlesnakes. The results may revolutionize the theory regarding the origin of type-II rattlesnakes and assist with the diagnosis and clinical management of G. intermedius bites. Furthermore, the possibility of using the currently available antivenoms of Neotropical rattlesnakes to treat G. intermedius bites seems feasible.
Subject(s)
Anticoagulants/chemistry , Crotalus , Crotoxin/chemistry , Neurotoxins/chemistry , Phospholipases A2/chemistry , Amino Acid Sequence , Animals , Anticoagulants/metabolism , Crotoxin/genetics , Crotoxin/metabolism , Humans , Mice , Molecular Sequence Data , Neurotoxins/genetics , Neurotoxins/metabolism , Phospholipases A2/genetics , Phospholipases A2/metabolism , Rabbits , Sequence Analysis, ProteinABSTRACT
In the alternating anaerobic/aerobic SBR reactor,the nitrification and denitrification characteristics of simultaneous nitrogen and phosphorus removal by granular sludge were studied. The results of batch experiments indicated that the maximal nitrification rate, denitrification rate, anoxic phosphorus uptake and denitrification rate were 14.13 mg x (g x h))-1), 34.89 mg x (g x h)/(-1) and 13.11 mg x (g x h)(-1), respectively. In SBR, the maximal nitrification rate and denitrification rate were 4.60 mg x (g x h)(-1) and 1.43 mg x (g x h)(-1), respectively, which were lower than those in the batch test. The amount of nitrogen removal by the simultaneous nitrification and denitrification process was approximately 232.5 mg x d(-1), which was 54.3% of the total nitrogen removal. The removal efficiency of N and P was about 90% and 95%, respectively. The simultaneous nitrogen and phosphorus removal by granular sludge showed high efficiency in nitrogen and phosphorus removal.
