Influence of soybean isolate on the formation of heterocyclic aromatic amines in roasted pork and its possible mechanism.

In this paper, the effects of soybean protein isolate (SPI) on the formations of five heterocyclic aromatic amines (HAAs) in roasted pork were investigated. The levels of all five HAAs improved upon addition of 2.5% of SPI (P < 0.05). With higher SPI dosage, the levels of HAA decreased after seeing an increase. Two HAAs (MeIQx and 4,8-DiMeIQx) were inhibited by 10.0% of SPI, with the inhibitory efficiencies of 7.0 % and 85.7%, respectively. After being heated, the levels of both the free amino acids and carbonyl groups in the SPI were observed significantly increased, from 55.04 µg g·SPI-1 to 91.66 µg g·SPI-1 and from 123.85 ± 13.07 to 931.78 ± 32.56, respectively (P < 0.05). Therefore, the possible promotion mechanism of the SPI was speculated that the heated SPI would provide both the HAA precursors and carbonyls, which significantly promoted the Strecker degradation and generated more HAA intermediates (P < 0.05).

[Identification of a high ammonia nitrogen tolerant and heterotrophic nitrification-aerobic denitrification bacterial strain TN-14 and its nitrogen removal capabilities].

A new strain of high ammonia nitrogen tolerant and heterotrophic nitrification-aerobic denitrification bacterium TN-14 was isolated from the environment. Its physiological and biochemical characteristics and molecular identification, performences of heterotrophic nitrification-aerobic, the abilities of resistance to ammonia nitrogen as well as the decontamination abilities were studied, respectively. It was preliminary identified as Acinetobacter sp. according to its physiological and biochemical characteristics and molecular identification results. In heterotrophic nitrification system, the ammonia nitrogen and total nitrogen removal rate of the bacterial strain TN-14 could reach 97.13% and 93.53% within 24 h. In nitrates denitrification system, the nitrate concentration could decline from 94.24 mg · L(-1) to 39.32 mg · L(-1) within 24 h, where the removal rate was 58.28% and the denitrification rate was 2.28 mg · (L · h)(-1); In nitrite denitrification systems, the initial concentration of nitrite could be declined from 97.78 mg · L(-1) to 21.30 mg x L(-1), with a nitrite nitrogen removal rate of 78.22%, and a denitrification rate of 2.55 mg · (L· h)(-1). Meanwhile, strain TN-14 had the capability of flocculant production, and the flocculating rate could reach 94.74% when its fermentation liquid was used to treat 0.4% kaolin suspension. Strain TN-14 could grow at an ammonia nitrogen concentration as high as 1200 mg · L(-1). In the aspect of actual piggery wastewater treatment by strain TN-14, the removal rate of COD, ammonia nitrogen, TN and TP cloud reached 85.30%, 65.72%, 64.86% and 79.41%, respectively. Strain TN-14 has a good application prospect in biological treatment of real high- ammonia wastewater.

[Piggery wastewater cultivating bioflocculant-producing flora B-737 and the fermentation characteristics].

Piggery wastewater was used as a cheap alternative medium for a bioflocculant-producing bacterial flora B-737. Effects of COD concent, addition of ammonium oxalate or phosphate on the cell growth and bioflocculant yield were investigated, and the fermentation kinetics was studied in the optimal culture media. The results showed that the piggery wastewater (COD was about 3000 mg x L(-1), TN was about 170 mg x L(-1)) had a suitable C/N ratio for the growth and fermentation of flora B-737, with addition of only 1.6 g x L(-1) K2HPO4 and 0.8 g x L(-1) KH2PO4, flora B-737 grew well and the bioflocculant yield reached 1.5 g x L(-1), in the meantime, the COD and TN of the wastewater was reduced by 61.9% and 53.6%, respectively. Not only was the medium cost reduced by over 90% , but it was a new way to recycle piggery wastewater. In addition, the dynamic models on cell growth and flocculants formation in the fermentation process of B-737 were established according to the equation of Logistic and Luedeking-Piret, respectively.