Trimethylamine (TMA) is a typical nitrogen-containing amine organic pollutant, and one of the main malodorous gases causing odor pollution in animal husbandry. This gas is a harmful gas with a strong fishy odor. It not only causes point-source pollution in farming areas, but also its long-term exposure poses potential health risks to humans, attracting people's attention in recent years.

This study aimed to screen high-efficiency TMA-removing strains with strong degradation ability by collecting large amounts of animal manure, for providing excellent strains for the prevention and control of TMA pollution in livestock farming.

In this study, efficient TMA-removing strains were screened from the manures of pigs and cows by the methods of enrichment culture, isolation, purification, and deodorization ability measurement. Then the strains were identified using morphological observation and 16S rRNA gene analysis to determine their taxonomic characteristics. On this basis, the effects of different pH values (5.0, 6.0, 7.0, 8.0, and 9.0), carbon sources (glucose, sucrose, fructose, maltose, and xylose), salinities (0, 0.5%, 1.0%, 1.5%, and 2.0%), and inoculum concentrations (1%, 5%, 10%, 15%, and 20%) on bacterial biomass were further investigated to define the optimal growth conditions for the strains. Moreover, the actual deodorization effect of the efficient strains was verified by investigating the release concentration and removal rate of TMA during the initial stage of feces fermentation.

(1) A total of 10 TMA-removing strains, named T1 to T10, were isolated from livestock manure, among which strain T2 (Bacillus subtilis) and strain T3 (Acinetobacter sp.) exhibited the highest removal abilities of TMA. The TMA-removing rates after 48 h of incubation reached 26.91% for T2 and 29.59% for T3, which were higher than those of the other eight strains (P < 0.05). (2) Different pH values, carbon sources, salinities, and inoculum concentrations exerted varying effects on the growth of strains T2 and T3. Optimal growth conditions for T2 were as follows: pH=6.0, glucose as carbon source, 0.5% NaCl, and inoculum concentration of 1%; for T3, pH=8.0, sucrose as carbon source, 0.5% NaCl, and inoculum concentration of 1%. Under these optimal conditions above, the strains exhibited the fastest growth rate and achieved the maximum biomass. (3) The verification test of deodorization effect showed that when the feces were supplemented with T2 or T3, the average release amounts of TMA were lower than those in the control group (P < 0.01), and the highest removal rates reached 42.65% for T1 and 39.63% for T2.

Bacillus subtilis (T2) and Acinetobacter sp. (T3) isolated in this study had a high-efficiency ability to remove TMA, and would possess potential utilization value in the field of livestock manure treatment and control of pollution in animal husbandry.

In view of the problem of odor non-point source pollution in fattening area of mutton sheep in recent years, the effects of bedding bed on growth performance of fattening lambs and odor components in the house were discussed, so as to provide technical path for odor emission reduction in fattening sheep house.

Two-hundred fifty healthy fattening lambs with similar weight and age were used and randomly divided into 5 groups according to different bedding materials, which were control group (plain soil), group A (full-sawdust), group B (furfural + sawdust), group C (rice husk + sawdust), and group D (corn cob + sawdust). The trial period was 90 days (d 1-45 in early period; d 46-90 in late period). The odor components in environment above and inside the litter bed were detected by using GC-MS method during different periods, and the effect of litter bed on production performance in fattening lambs was also analyzed.

(1) Compared with the control group, the four groups with litter bed demonstrated an increase in daily feed intake (P<0.05), which was increased by 7.7% in group A and 8.7% in Group B, 12.1% in Group C, and 7.8% in Group D. However, the daily gain and ratio of feed to gain exhibited no difference (P>0.05). (2) Nine kinds and eight kinds of odor components were detected throughout test period above litter bed and inside litter bed, respectively, and the components consisted of 31 kinds of volatile organic compounds (VOCs), including 4 alcohols, 10 alkanes, 3 amines, 1 phenol, 7 esters, 4 ketones, 2 aldehydes, 3 acids, and 1 thiol. The odor kinds detected in 4 litter groups were basically same as the control group. (3) From content analysis of odor components, the alkane content was the highest with 52.0%-77.5% among all odor components, no matter experimental period or detected space; however, no difference was observed among all groups (P>0.05). Also, the content of phenol or amine in litter groups demonstrated a decrease (P<0.05) in two detected spaces in early and late periods, compared with the control, exhibiting the decrease in group C was obvious. Besides, the content of alcohol, amine, or phenol was higher (P<0.05) in early period than that in late period both upper and inner spaces of litter bed; however, the ester content in late period was higher (P<0.05) than that in early period. (4) During entire experimental period, four kinds of key odor-causing substances were detected both in upper and inner of litter bed, including 2-ethylhexanol, N,N-dimethylacetamide, phenol, and 1 H-indole-3-thiol. For the contents of the four odor-causing components, each litter group showed a decreasing trend, compared with the control group, and the decrease in group C was the most obvious (P<0.05).

In summary, four combined litter beds in this study could improve growth performance in fattening lambs, and decrease odor content in environment. The results would provide a technical pathway for reduction of odor emission in sheep barn.

Odor pollution from animal industry has become a pain point and a difficulty in recent years. Ammonia (NH₃) is an important harmful gas with great contribution rate to odor pollution, and its cutting emission becomes an urgent task. The objective of this study was to isolate the efficient NH₃-removing strains and to optimize its cultivated conditions, which would provide excellent strains for developing deodorizers.

Manure deposited in the sewage outlet of the farm was collected as the source of strain isolation. The NH₃-removing strains were enriched, separated, and purified using NH₃ enrichment culture medium. Then, the degradation ability of purified bacteria above was determined using NH₃-degradating culture medium, and the efficient NH₃-removing strains were screened. The isolated strains were identified by morphology (colony morphology and Gram staining) and 16S rRNA sequencing method. Further, the effects of various cultivated conditions on biomass of the strains, including pH (5.0, 6.0, 7.0, 8.0, and 9.0), carbon sources (xylose, sucrose, fructose, maltose, and glucose), salt contents (0%, 0.5%, 1.0%, 1.5%, and 2.0%), and inoculum amounts (1.0%, 5.0%, 10%, 15%, and 20%), were performed, and the optimal conditions were determined.

(1) A total of 12 suspected NH₃-degrading strains were isolated by enrichment culture (named as C1-C12), among of which, the strain named C5 had efficient NH₃-removing ability. The logarithmic growth period of the strain C5 was 2 to 20 h. During the period, the degradation rate of C5 increased with the growing bacteria biomass, reaching 60.70% at 24 h and 75.49% at 48 h of culture, respectively, which was greater than that of the other 11 strains in the same time (P<0.05). From morphology and 16S rRNA identification, the C5 was characterized by stubby- and rod-shaded, pointless round at both ends, and no capsule, as well as Gram-negative bacteria. Combined with gene sequencing results and phylogenetic tree, the C5 was determined to be Klebsiella pneumoniae. (2) Various pH values, carbon sources, salt content, and inoculation amount showed different effects on the concentration of C5 after 48 h of culture. The C5 concentration at pH 7.0 was greater than that at pH 5.0, pH 6.0 and pH 9.0 (P<0.05). Compared with other carbon sources, the C5 concentration for glucose as carbon source was the greatest during the culture period of 8 to 48 h. Under different salt content and inoculation amount, there were differences (P<0.01) in bacterial concentration between groups, exhibiting the greatest concentration of bacterial solution at 1.5% salt and a peak value at 40 h of culture. Besides, the fast growth of bacteria was observed for 1.0% of inoculation amount and bacterial concentration increased, compared with other inoculation amounts. Therefore, the optimal growing conditions of the C5 were as follows: pH=7.0, carbon source of glucose, 1.5% salt content, and 1.0% of inoculum amount, where the growth rate and biomass of the C5 were optimal.

Klebsiella pneumoniae (strain C5) isolated from manure possessed the ability to remove NH₃ efficiently, which would have potential utilization value in livestock manure treatment.