Study on the mechanism of co-pyrolysed biochar on soil DOM evolution in short-term cabbage waste decomposition.

Cabbage waste returned soil was studied to assess the short-term influences of the application of cabbage waste biochar (CB), pine wood biochar (PB), and co-pyrolysed biochar (PCB) on soil dissolved organic matter (DOM) evolution. The decrease in DOM and soil organic matter (SOM) content was greater in the biochar-added soils during 35 days of decomposition. The DOM and SOM content in PCB added group decreased by 26.96 mg L-1 and 4.48 g kg-1, respectively. The increase in relative abundance of humic acid-like substances in DOMs was higher in the biochar-added soils during decomposition, which increased by 4.29% in PCB added group. PCB addition also resulted in a high SOM content (initial content of 78.82 g kg-1), and mineral elements were introduced into the soil, thus increasing soil pH (7.81) and electrical conductivity (574.67 µs cm-1). Moreover, the addition of biochars attenuated the decrease in average relative abundance of Bacillaceae and promoted bacterial proliferation during decomposition. The application of biochars regulated the soil bacterial community and promoted organic matter conversion and soil DOM evolution.

Screening and identification of lactic acid bacteria with antimicrobial abilities for aquaculture pathogens in vitro.

This study aimed to evaluate the antibacterial properties of nine lactic acid bacterial strains. The agar diffusion method (Oxford cup method) was used to assess the antimicrobial activity against pathogenic bacteria in aquaculture. The results showed that all selected strains inhibited the growth of Photobacterium damsel, Vibrio alginolyticus, Listonella anguillarum, Edwardsiella ictaluri, Aeromonas hydrophila, V. arahaemolyticus, Edwardsiella tarda and V. harveyi, but did not inhibit the growth of Metschnikowia bicuspidata. Among these strains of lactic acid bacteria, r1 was selected for its obvious antibacterial activity against eight kinds of pathogenic bacteria by 96-well plate method. Its inhibitory rate reached 96%, and it could inhibit the growth of six pathogenic bacteria at 121 â„ƒ, 20 min and pH 3.5-4.0. It was identified as Lactiplantibacillus plantarum by morphological observation and 16S rRNA sequencing analysis. Because strain r1 was isolated from culture ponds and exerted strong inhibitory effects on pathogenic bacteria, it holds potential as an agent to prevent and control infectious diseases in aquaculture. This study provides a foundation for the development and utilization of probiotics in aquaculture.

Nitrogen Removal Performance of Novel Isolated Bacillus sp. Capable of Simultaneous Heterotrophic Nitrification and Aerobic Denitrification.

The control of nitrogenous pollutants is a key concern in aquaculture production. Bacillus spp. are commonly used as probiotics in aquaculture, but only a few reports have focused on the simultaneous heterotrophic nitrification and aerobic denitrification (SND) capacity of Bacillus sp. strains. In order to improve nitrogen biodegradation efficiency in the aquaculture industry, the SND capacity of Bacillus sp. strains was evaluated using both individual and mixed nitrogen sources and different sources of organic carbon. Twelve Bacillus sp. isolates were screened from aquaculture pond sediments and shrimp guts for nitrogen biodegradation. Six strains exhibited especially efficient inorganic nitrogen removal capacities in media with individual and mixed nitrogen sources. These strains comprise K8, N2, and N5 (B. subtilis), HYS (B. albus), H4 (B. amyloliquefaciens), and S1 (B. velezensis). The strains grew better when the sole nitrogen source was NH4+-N, but degraded nitrogen in the following order: nitrite nitrogen (NO2--N), ammonium nitrogen (NH4+-N), and nitrate nitrogen (NO3--N). There was no associated NO2--N accumulation, regardless of the nitrogen source. The optimal carbon source for nitrogen removal varied based on different nitrogen sources and associated metabolic pathways. The optimal carbon sources for the removal of NO3--N, NO2--N, and NH4+-N were sodium citrate, sodium acetate, and sucrose, respectively. The application of H4 in recirculating aquaculture water further demonstrated that NO2--N and NH4+-N could be effectively removed. This study thus provides valuable technical support for the bioremediation of aquaculture water.

Deciphering the extracellular and intracellular antibiotic resistance genes in multiple environments reveals the persistence of extracellular ones.

The extracellular and intracellular antibiotic resistance genes (eARGs and iARGs) together constitute the entire resistome in environments. However, the systematic analysis of eARGs and iARGs was still inadequate. Three kinds of environments, i.e., livestock manure, sewage sludge, and lake sediment, were analyzed to reveal the comprehensive characteristics of eARGs and iARGs. Based on the metagenomic data, the diversities, relative abundances, and compositions of eARGs and iARGs were similar. The extracellular and intracellular integrons and insertion sequences (ISs) also did not show any significant differences. However, the degree and significance of the correlation between total relative abundances of integrons/ISs and ARGs were lower outside than inside the cells. Gene cassettes carried by class 1 integron were amplified in manure and sludge samples, and sequencing results showed that the identified ARGs extracellularly and intracellularly were distinct. By analyzing the genetic contexts, most ARGs were found located on chromosomes. Nevertheless, the proportion of ARGs carried by plasmids increased extracellularly. qPCR was employed to quantify the absolute abundances of sul1, sul2, tetO, and tetW, and their extracellular proportions were found highest in sludge samples. These findings together raised the requirements of considering eARGs and iARGs separately in terms of risk evaluation and removal management.

Simultaneous heterotrophic nitrification and aerobic denitrification by a novel isolated Pseudomonas mendocina X49.

Six bacterial strains with simultaneous nitrification-denitrification abilities were isolated from a Beijing sewage treatment plant to improve nitrogen biodegradation efficiency. One of these strains, X49, was identified as Pseudomonas mendocina, and was characterized as the best strain with which to rapidly degrade a high concentration of inorganic nitrogen. X49 completely converted 5-100 mg.L-1 of ammonia in 12 h, with no nitrite accumulation; the maximum removal rate of 26.39 mg (N).L-1.h-1 was achieved between 4 h and 6 h. In 16 h, the strain removed 100 mg.L-1 nitrite and 72.61 mg.L-1 nitrate under aerobic conditions, at degredation rates which reached 4.54 and 6.25 mg (N).L-1.h-1, respectively. Our results suggest that P. mendocina X49 achieved efficient and simultaneous nitrification and denitrification ability under heterotrophic aerobic conditions.

Breeding of high protein Chlorella sorokiniana using protoplast fusion.

To improve Chlorella's economic viability as a natural bait in aquaculture, protoplast fusion technology was used for two Chlorella mutants, H10 and Z13, selected by UV and chemical mutagenesis. Chlorella sorokiniana protoplast was prepared using the enzyme method, and then the optimal enzyme combination of 4% cellulase and 2% driselase was screened out. Z13 and H10 protoplast preparation rates reached 34.72% and 31.11%, respectively. Nine fusions with higher growth rates were selected to assess their biomass, total and soluble proteins contents. Dry cell weight, total protein, and soluble protein of fusion R7 were 0.92 g.L-1, 67.16%, and 0.59 mg.g-1, respectively. The biomass was 1.59, 1.43 times that of H10 and Z13; total and soluble proteins increased by 8.89%, 10.25% and 50.12%, 74.62% respectively, compared with the original algae. These results have implications for breeding excellent strains, and for large-scale and optimal application of Chlorella in aquaculture.

[Isolation, identification and fermentation optimization of lactic acid bacteria for aquaculture water purification].

Objective: In order to get excellent strains for aquiculture water purification, we screened lactic acid bacteria from the aquaculture environment and intestinal tract of shrimp. Methods: The potential water purification ability of lactic acid bacteria at normal and low temperature was evaluated in the simulated wastewater. Morphological physio-biochemical characteristics, 16S rRNA gene sequence analysis were used to identify strain r13. Single factor test and orthogonal-design experiment were applied to optimize fermentation for r13. Results: In total 136 lactic acid bacteria strains were isolated from 3 samples. The results of water purification test suggested r13 had higher removal ability of nitrite and ammonia from water. After 72 h treatment by r13, nitrite with 11.5 mg/L in the water was completely removed and ammonia degradation rate was 29.1% with 13.0 mg/L original concentration. According to morphological, physio-biochemical characteristics and 16S rRNA gene sequence analysis, r13 was identified as Lactobacillus plantarum. The optimal fermentation condition for r13 was 6.0 g/L yeast extract, 20.0 g/L glucose, 4.0 g/L sodium acetate, 2.0 g/L diammonium hydrogen citrate, 2.0 g/L monopotassium phosphate, 50 mL tomato juice, with inoculation rate 5% (V/V), at pH 6.0 and 34℃. Under this condition cultured for 72 h, the bacterial biomass reached 28.4 g/L wet weight and cell counting reached 4.4×109 CFU/mL. Conclusion: Considering high nitrite removal ability, we suggested that r13 would be promising microorganism for water purification in aquiculture.

[Isolation, screening and identification of yeast for aquaculture water purification].

OBJECTIVE: In order to get excellent yeast strains for aquiculture water purification, we isolated, screened and identified yeasts from the aquacultural environment and intestinal tract of shrimp. METHODS: The potential water purification ability of yeasts, isolated from the activated sludge of aquacultural environment and intestinal tract of white shrimp and mantis shrimp under normal and low temperature, was evaluated in the simulated wastewater. Morphological physio-biochemical characteristics, 5.8S rDNA ITS gene sequence analysis were used to identify the strains. RESULTS: Thirty-seven yeast strains were isolated from 3 samples, among them 16 strains were isolated under normal temperature (25 °C) while 21 strains were isolated under low temperature (15° C). Water purification test suggested 5 strains isolated under 25 °C and 6 strains isolated under 15 °C had higher removal ability of nitrite and ammonia from water. After 48 hours treatment with DN9 and CN6, 10.64 mg/L nitrite in the water was completely removed. After 96 hours treatment, CODcr degradation rates of the 2 strains were 52% and 67%, respectively. According to morphological, physio-biochemical characteristics and 5.8S rDNA ITS gene sequence analysis, the strain DN9 was identified as Rhodotorula mucilaginosa and CN6 as Rhodosporidium paludigenum. CONCLUSION: Strains DN9 and CN6 would be promising for water purification in aquiculture.

Using Bacillus amyloliquefaciens for remediation of aquaculture water.

Remediation of aquaculture water using microorganisms like Bacillus species is a burgeoning trend for the sustainable development of aquaculture industries. In this work, a Bacillus amyloliquefaciens strain (namely B. amyloliquefaciens HN), isolated from activated sludge of a polluted river, was evaluated for its potential in water remediation using simulated aquaculture water. B. amyloliquefaciens HN exhibited high tolerance towards 80 mg l(-1) of nitrite-N and ammonia-N. It could effectively remove 20 mg l(-1) of nitrite-N, but was inefficient in eliminating ammonia-N when the ammonia-N concentration was below 20 mg l(-1). Further studies showed that the ammonia-N removal by B. amyloliquefaciens HN was more efficient at 30°C and 35°C than 25°C, and that maximum nitrite-N removal rate was achieved at pH 8.