Dynamic analysis of the microbial communities and metabolome of healthy banana rhizosphere soil during one growth cycle.

Background: The banana-growing rhizosphere soil ecosystem is very complex and consists of an entangled network of interactions between banana plants, microbes and soil, so identifying key components in banana production is difficult. Most of the previous studies on these interactions ignore the role of the banana plant. At present, there is no research on the the micro-ecological environment of the banana planting growth cycle. Methods: Based on high-throughput sequencing technology and metabolomics technology, this study analyzed the rhizosphere soil microbial community and metabolic dynamics of healthy banana plants during one growth cycle. Results: Assessing the microbial community composition of healthy banana rhizosphere soil, we found that the bacteria with the highest levels were Proteobacteria, Chloroflexi, and Acidobacteria, and the dominant fungi were Ascomycota, Basidiomycota, and Mortierellomycota. The metabolite profile of healthy banana rhizosphere soil showed that sugars, lipids and organic acids were the most abundant, accounting for about 50% of the total metabolites. The correlation network between fungi and metabolites was more complex than that of bacteria and metabolites. In a soil environment with acidic pH, bacterial genera showed a significant negative correlation with pH value, while fungal genera showed no significant negative correlation with pH value. The network interactions between bacteria, between fungi, and between bacteria and fungi were all positively correlated. Conclusions: Healthy banana rhizosphere soil not only has a stable micro-ecology, but also has stable metabolic characteristics. The microorganisms in healthy banana rhizosphere soil have mutually beneficial rather than competitive relationships.

Risk of congenital heart disease due to exposure to common electrical appliances during early pregnancy: a case-control study.

To examine the association between exposure to common electrical appliances in early pregnancy and congenital heart disease (CHD). A case-control study of 2339 participants was conducted in six hospitals in Xi'an, Shaanxi Province, Northwest China from 2014 to 2016. All infants with CHD were diagnosed according to ICD-10 classification. Selected controls consisted of newborns from the same hospital, without any birth defects, and 1:3 matched by birthdate. We conducted personal interviews with the mothers to gather information on any exposure to electrical appliances during pregnancy. Multivariate logistic regression was used to estimate the effects of exposure to common electrical appliances on CHD. We observed that the mothers exposed to computers (OR: 1.33, 95% CI: 1.03, 1.71), induction cookers (OR: 2.79, 95% CI: 2.19, 3.55), and microwave ovens (OR: 1.53, 95% CI: 1.01, 2.31) during early pregnancy were more likely to give birth to infants with CHD. Mothers who wore radiation protection suits (OR: 0.67, 95% CI: 0.52, 0.87) during early pregnancy decreased the risk of CHD in their neonate. There was an interaction for induction cooker exposure with wore radiation protection suits on CHD (RERI: - 1.44, 95% CI: - 2.48, - 0.39; S: 0.37, 95% CI: 0.16, 0.84; AP: - 0.79, 95% CI: - 1.53, - 0.05). Our study confirmed that exposure to some electrical appliances was associated with a higher risk of CHD, and wearing a radiation protection suit was associated with a lower risk of CHD. Women should therefore reduce the usage of electrical appliances before and during pregnancy.

Identification of an acidic endo-polygalacturonase from Penicillium oxalicum CZ1028 and its broad use in major tropical and subtropical fruit juices production.

Endo-polygalacturonases play an important role on depectinization in fruit juices industry. A putative endo-polygalacturonase gene PoxaEnPG28A was cloned from Penicillium oxalicum CZ1028. PoxaEnPG28A consisted of a putative signal peptide and a catalytic domain belonging to glycoside hydrolase family 28, and it shared 72% identity with that of a functionally characterized endo-polygalacturonase from Trichoderma harzianum. Gene PoxaEnPG28A was successfully expressed in Pichia pastoris with a high yield of 1828.7 U/mL. The purified recombinant enzyme PoxaEnPG28A hydrolyzed polygalacturonic acid in endo-manner releasing oligo-galacturonates. PoxaEnPG28A showed maximal activity at pH 5.5 and 55°C, and was stable between pH 3.0 to 10.0 and below 45°C. The kinetic constants Km and Vmax of PoxaEnPG28A were calculated as 1.57 g/L and 14,641.29 U/mg, respectively. PoxaEnPG28A significantly improved the yields of fruit juices from banana, plantain, papaya, pitaya and mango. The high production level of the recombinant enzyme PoxaEnPG28A by P. pastoris and remarkable catalytic activity of PoxaEnPG28A toward five kinds of fruit juices made the enzyme a potential application in agriculture and food industries.

Succinic acid production from duckweed (Landoltia punctata) hydrolysate by batch fermentation of Actinobacillus succinogenes GXAS137.

Duckweed is potentially an ideal succinic acid (SA) feedstock due to its high proportion of starch and low lignin content. Pretreatment methods, substrate content and nitrogen source were investigated to enhance the bioconversion of duckweed to SA and to reduce the costs of production. Results showed that acid hydrolysis was an effective pretreatment method because of its high SA yield. The optimum substrate concentration was 140g/L. The optimum substrate concentration was 140g/L. Corn steep liquor powder could be considered a feasible and inexpensive alternative to yeast extract as a nitrogen source. Approximately 57.85g/L of SA was produced when batch fermentation was conducted in a 1.3L stirred bioreactor. Therefore, inexpensive duckweed can be a promising feedstock for the economical and efficient production of SA through fermentation by Actinobacillus succinogenes GXAS137.

Optimization of medium composition for cis,cis-muconic acid production by a Pseudomonas sp. mutant using statistical methods.

cis,cis-Muconic acid (CCMA) is used as a platform chemical for the production of several high-value compounds. For this article, an optimization strategy has been used to optimize medium composition for CCMA production from fairly cheap benzoate by Pseudomonas sp. 1167. The effect of different concentrations of medium components on CCMA production was studied. CCMA yields obtained from Plackett-Burman design (PBD) showed wide variation (3.95-5.87 g/L), and the first-order model indicated that (NH(4))(2)SO(4) (P < 0.01) and K(2)HPO(4) · 3H(2)O (P < 0.02) were the significant components for CCMA production. Then the optimization was performed by steepest ascent design (SAD) and central composite design (CCD), and a validation experiment was conducted to verify the predicted value. The optimal medium composition was: 12 g/L sodium benzoate, 2.5 g/L sodium succinate, 0.7932 g/L (NH(4))(2)SO(4), 1.5612 g/L K(2)HPO(4) · 3H(2)O, 1.2 g/L MgSO(4) · 7H(2)O, 0.4 g/L yeast extract, 0.08 g/L FeCl(3) · 6H(2)O, and 0.08 g/L ethylenediamine tetraacetic acid (EDTA). Under these conditions, a maximum of 7.18 g/L CCMA was produced per 12 g/L benzoate with a highly efficient process within 11 hr and a molecular conversion yield of 61%. Altogether, our results provide valuable insights into nutritional supplementation of CCMA production by using statistical methods, which may benefit a cost-competitive industrial fed-batch fermentation process using a cheap substrate.

[Optimization of succinic acid fermentation with Actinobacillus succinogenes by response surface methodology].

Succinic acid is an important C4 platform chemical in the synthesis of many commodity and special chemicals. In the present work, different compounds were evaluated for succinic acid production by Actinobacillus succinogenes GXAS 137. Important parameters were screened by the single factor experiment and Plackeet-Burman design. Subsequently, the highest production of succinic acid was approached by the path of steepest ascent. Then, the optimum values of the parameters were obtained by Box-Behnken design. The results show that the important parameters were glucose, yeast extract and MgCO3 concentrations. The optimum condition was as follows (g/L): glucose 70.00, yeast extract 9.20 and MgCO3 58.10. Succinic acid yield reached 47.64 g/L at the optimal condition. Succinic acid increased by 29.14% than that before the optimization (36.89 g/L). Response surface methodology was proven to be a powerful tool to optimize succinic acid production.

Cloning, expression and identification of a new trehalose synthase gene from Thermobifida fusca genome.

A new open reading frame in Thermobifida fusca sequenced genome was identified to encode a new trehalose synthase, annotated as "glycosidase" in the GenBank database, by bioinformatics searching and experimental validation. The gene had a length of 1830 bp with about 65% GC content and encoded for a new trehalose synthase with 610 amino acids and deduced molecular weight of 66 kD. The high GC content seemed not to affect its good expression in E. coli BL21 in which the target protein could account for as high as 15% of the total cell proteins. The recombinant enzyme showed its optimal activities at 25 degrees and pH 6.5 when it converted substrate maltose into trehalose. However it would divert a high proportion of its substrate into glucose when the temperature was increased to 37 degrees, or when the enzyme concentration was high Its activity was not inhibited by 5 mM heavy metals such as Cu2+, Mn2+, and Zn2+ but affected by high concentration of glucose. Blasting against the database indicated that amino acid sequence of this protein had maximal 69% homology with the known trehalose synthases, and two highly conserved segments of the protein sequence were identified and their possible linkage with functions was discussed.