The effect of combined application of biochar and phosphate fertilizers on phosphorus transformation in saline-alkali soil and its microbiological mechanism.

This study investigated the effects of combining Phragmites australis-based biochar, prepared at 400 °C, with various types of phosphate fertilizers-soluble, insoluble, and organic-on the content and transformation of phosphorus fractions in saline-alkali soil. Additionally, we explored microbiological mechanisms driving these transformations. The results showed that this combination significantly increased the concentrations of dicalcium phosphate (Ca2P), octacalcium phosphate (Ca8P), aluminum phosphate (AlP), moderately labile organic phosphorus (MLOP), and resistant organic phosphorus (MROP) in soil. Conversely, the levels of hydroxyapatite (Ca10P) and highly resistant organic phosphorus (HROP) decreased. The increase in labile organic phosphorus (LOP) content or decrease in iron phosphate (FeP) was found to effectively enhance the availability of Olsen phosphorus (Olsen-P) in soil. Furthermore, the study revealed that biochar mixed with organic phosphate fertilizers increased the activity of soil acid phosphatase (ACP) and neutral phosphatase (NEP), while reducing alkaline phosphatase (ALP) activity. In contrast, biochar combined with soluble and insoluble phosphate fertilizers decreased the activity of ACP (22.59 % and 28.57 %, respectively) and NEP (62.50 % and 11.11 %, respectively), with the combination with insoluble fertilizers also reducing ALP activity by 55.84 %, whereas the soluble combination increased it by 190.34 %. Additionally, the co-application of biochar and phosphate fertilizers altered the composition and abundance of the gene phoD-harboring microbial community, enhancing the abundance of Proteobacteria and reducing that of Actinobacteria. Correlation analysis between phoD-functional microbial species and various phosphorus fractions showed that Rhodopseudomonas was significantly associated with several phosphorus components, exhibiting a positive correlation with Ca2P, Ca8P, AlP, LOP, MLOP, and MROP, but a negative relationship with Ca10P. These findings suggest that the combined application of biochar and phosphate fertilizers could change the abundance of Rhodopseudomonas, potentially influencing phosphorus cycling in the soil. This research provides a strong scientific foundation for the efficient combined use of biochar and phosphate fertilizers in managing saline-alkali soil.

Structure changes of lignin and their effects on enzymatic hydrolysis for bioethanol production: a focus on lignin modification.

Enzymatic hydrolysis contributes to obtaining fermentable sugars using pretreated lignocellulose materials for bioethanol generation. Unfortunately, the pretreatment of lignocellulose causes low substrate enzymatic hydrolysis, which is due to the structure changes of lignin to produce main phenolic by-products and non-productive cellulase adsorption. It is reported that modified lignin enhances the speed of enzymatic hydrolysis through single means to decrease the negative effects of fermentation inhibitors or non-productive cellulase adsorption. However, a suitable modified lignin should be selected to simultaneously reduce the fermentation inhibitors concentration and non-productive cellulase adsorption for saving resources and maximizing the enzymatic hydrolysis productivity. Meanwhile, the adsorption micro-mechanisms of modified lignin with fermentation inhibitors and cellulase remain elusive. In this review, different pretreatment effects toward lignin structure, and their impacts on subsequent enzymatic hydrolysis are analyzed. The main modification methods for lignin are presented. Density functional theory is used to screen suitable modification methods for the simultaneous reduction of fermentation inhibitors and non-productive cellulase adsorption. Lignin-fermentation inhibitors and lignin-cellulase interaction mechanisms are discussed using different advanced analysis techniques. This article addresses the gap in previous reviews concerning the application of modified lignin in the enhancement of bioethanol production. For the first time, based on existing studies, this work posits the hypothesis of applying theoretical simulations to screen efficient modified lignin-based adsorbents, in order to achieve a dual optimization of the detoxification and saccharification processes. We aim to improve the integrated lignocellulose transformation procedure for the effective generation of cleaner bioethanol.

Potential mechanism of biochar enhanced degradation of oxytetracycline by Pseudomonas aeruginosa OTC-T.

Extensive use of oxytetracycline (OTC) and the generation of its corresponding resistance genes have resulted in serious environmental problems. Physical-biological combined remediation is an attractive method for OTC degradation because of its high remediation efficiency, stability, and environmental friendliness. In this study, an effective OTC-degrading strain identified as Pseudomonas aeruginosa OTC-T, was isolated from chicken manure. In the degradation experiment, the degradation rates of OTC in the degradation systems with and without the biochar addition were 92.71-100 % and 69.11-99.59 %, respectively. Biochar improved the tolerance of the strain to extreme environments, and the OTC degradation rate increased by 20.25 %, 18.61 %, and 13.13 % under extreme pH, temperature, and substrate concentration conditions, respectively. Additionally, the degradation kinetics showed that biochar increased the reaction rate constant in the degradation system and shortened the degradation period. In the biological toxicity assessment, biochar increased the proportion of live cells by 17.63 % and decreased the proportion of apoptotic cells by 58.87 %. Metabolomics revealed that biochar had a significant effect on the metabolism of the strains and promoted cell growth and reproduction, effectively reducing oxidative stress induced by OTC. This study elucidates how biochar affects OTC biodegradation and provides insights into the future application of biochar-assisted microbial technology in environmental remediation.

The transformation of heavy metal speciation during rapid high-temperature aerobic fermentation of food waste and their potential mechanisms.

In this study, the content changes of multiple trace heavy metals (HMs) in food waste using a new rapid high-temperature aerobic fermentation (RTAF) technology and their relationships with different physicochemical factors were researched. The results indicated that the content of HMs in the decomposed products met the industry standards for organic fertilizers (NY/T525-2021, China). Physicochemical factors played an important role in controlling the changes in HM content. The component evolution of dissolved organic matter was studied, and its influences on the transformation of HM speciation showed that the RTAF process converted proteins into humus-like substances. Redundancy analysis revealed that the main factors driving the speciation transformation of HMs were tyrosine-like substances or microbial-derived humus (C3), molecular weight of dissolved organic matter (SUVA254) and humification degree (E250/E365). The increase in humification degree contributed to passivating HMs. The correlation network analysis results showed that the exchangeable HMs (Exc-HMs) were related to Lactobacillus and Pediococcu. Additionally, the cytoskeleton, coenzyme transport and metabolic function of microorganisms affected the Exc-HM content. These research results can provide a scientific basis for the prevention and control of HM pollution during the treatment of food waste.

Biochar-assisted degradation of oxytetracycline by Achromobacter denitrificans and underlying mechanisms.

Contamination of the environment with large amounts of residual oxytetracycline (OTC) and the corresponding resistance genes poses a potential threat to natural ecosystems and human health. In this study, an effective OTC-degrading strain, identified as Achromobacter denitrificans OTC-F, was isolated from activated sludge. In the degradation experiment, the degradation rates of OTC in the degradation systems with and without biochar addition were 95.01-100% and 73.72-99.66%, respectively. Biochar promotes the biodegradation of OTC, particularly under extreme environmental conditions. Toxicity evaluation experiments showed that biochar reduced biotoxicity and increased the proportion of living cells by 17.36%. Additionally, biochar increased the activity of antioxidant enzymes by 34.1-91.0%. Metabolomic analysis revealed that biochar promoted the secretion of antioxidant substances such as glutathione and tetrahydrofolate, which effectively reduced oxidative stress induced by OTC. This study revealed the mechanism at the molecular level and provided new strategies for the bioremediation of OTC in the environment.

Preparation of a new biochar-based microbial fertilizer: Nutrient release patterns and synergistic mechanisms to improve soil fertility.

The contradiction between population growth and soil degradation has been increasingly prominent, such that novel fertilizers (e.g., biochar and microbial fertilizers) should be urgently developed. Biochar is a promising fertilizer carrier for microbial fertilizers due to its porous structure. However, the preparation and mechanisms of the effects of biochar-based microbial fertilizers have been rarely investigated. In this study, biochar, Bacillus, and exogenous N-P-K fertilizers served as the raw materials to prepare biochar-based microbial fertilizers (BCMFs) by optimizing the preparation methods and the process parameters. Moreover, the release patterns of N-P-K were analyzed. A pot experiment was performed on pakchoi to examine the effect of the BCMFs and explore its synergistic effect on soil fertility. The results of this study indicated that adsorption by biochar maintained bacterial activity, whereas the granulation process reduced bacterial activity. The adsorption-granulation process increased the content of total nitrogen and organic matter in the soil while enhancing the slow-release effect of the BCMFs. The Elovich model was capable of describing the nitrogen release of the BCMFs, including the diffusion and chemical processes. As indicated by the result of the column leaching experiment, the BCMFs stopped nutrient leaching more significantly than the conventional fertilizers (CF), especially in stopping N and P leaching. The use of the BCMFs improved the available soil nutrients and soil quality while enhancing the abundance of bacteria correlated with carbon and nitrogen metabolism in the soil. Moreover, a 20 % reduction in the use of the BCMFs did not significantly affect the soil available N and P and the growth status of pakchoi. The result of redundancy analysis indicated that the cation exchange capacity (CEC), NH4+-N, NO3--N, ß-glucosidase (BG), urease (URE), and alkaline phosphatase (AlkP) were the six critical environmental factors for the microbial community structure and could explain 94.8 % of the variance. The BCMFs up-regulated the levels of the above six factors, especially CEC and BG, thus improving the soil quality and enhancing the soil fertility.

Insights into ferulic acid detoxification mechanism by using a novel adsorbent, AEPA250: The microinteraction of ferulic acid with AEPA250 and Saccharomyces cerevisiae.

In this study, a novel adsorbent, Air Environment-prepared Adsorbent at 250 â„ƒ (AEPA250), was used to detoxify the main fermentation inhibitor (ferulic acid) present in the alkali-pretreated hydrolysate. AEPA250 reduced the effective concentration of ferulic acid by its adsorption, thereby decreasing the possible interaction of ferulic acid with Saccharomyces cerevisiae. The results indicated that AEPA250 functionalized with hydroxyl, carboxyl, and amino groups under acidic conditions with higher binding energies (-45.667, -27.046, and -11.008 kcal mol-1, respectively) and electronic cloud overlap and shorter bond distances (1.015, 1.010, and 2.094 Å, respectively) than those under the other pH conditions. These differences revealed that the electrostatic interaction dominated ferulic acid adsorption on AEPA250. Additionally, under acidic conditions and for carboxyl group functionalized AEPA250, energy band gap values of Eg1 were higher than those of Eg2, indicating that ferulic acid provided the π-electrons for the π-π electron donor-acceptor interactions with AEPA250. Furthermore, ferulic acid detoxification after AEPA250 adsorption caused the regulation of YDR316W-B and YPR137C-B genes of S. cerevisiae. These results might contribute to the development of other more efficient adsorbents and pretreatment methods and allow yeast engineering for improving the scale-up and self-sufficient production of bioethanol in the future.

Adsorption of ferulic acid from an alkali-pretreated hydrolysate using a new effective adsorbent prepared by a thermal processing method.

A new adsorbent (AEPA250) was prepared using the enzymatic hydrolyzed residue of rice straw in an air environment at 250 ℃ by a thermal processing method. Compared to the commercial adsorbent, AEPA250 possessed a larger specific surface area of 277.680 m2 g-1, and the maximum adsorption efficiency of ferulic acid from alkali-pretreated hydrolysate of rice straw achieved 70.33 % at the optimum conditions. Adsorption kinetics and isotherm studies showed that the pseudo second-order (PSO) (0.997 ≤ R2 ≤ 0.999) and Liu models (0.931 ≤ R2 ≤ 0.997) exhibited better fitting results, which indicated that chemical and saturable adsorption existed between ferulic acid and AEPA250. An adsorption thermodynamics study revealed the spontaneous and endothermic adsorption process (ΔHo > 0 and ΔSo< 0). Micropore diffusion was defined as the major adsorption rate-limiting step according to the analysis of Webber-Morris and Bangham's model. Additionally, π-π*, ion exchange, hydrogen bonding and precipitation were recognized as the four main mechanisms of ferulic acid removal by AEPA250 through SEM/EDX, EDX mapping, XPS, FTIR and XRD analysis. These results indicated that AEPA250 was effective for adsorbing inhibitors in pretreated rice straw hydrolysates, and it has high potential for application in establishing the self-sufficient production process of bioethanol.

Quantitative Structure-Toxicity Relationship analysis of combined toxic effects of lignocellulose-derived inhibitors on bioethanol production.

This study performed a Quantitative Structure-Toxicity Relationship (QSTR) model to evaluate the combined toxicity of lignocellulose-derived inhibitors on bioethanol production. Compared with all the control groups, the combined systems exhibited lower conductivity values, higher oxidation-reduction potential values, as well as maximum inhibition rates. These results indicated that the presence of combined inhibitors had a negative effect on the bioethanol fermentation process. Meanwhile, QSTR model was excellent for evaluating the combined toxic effects at lower ferulic acid concentration (([1:4] × IC50)) and (([1:1] × IC50)), due to higher R2 values (0.994 and 0.762), lower P values (0.000 and 0.023) and relative error values (less than 30%). The obtained results also showed that the combined toxic effects of ferulic acid and representative lignocellulose-derived inhibitors were relevant to different molecular descriptors. Meanwhile, the interactions of combined inhibitors were weaker when ferulic acid was at low concentration ([1:4] × IC50).

Toxicity evaluation of lignocellulose-derived phenolic inhibitors on Saccharomyces cerevisiae growth by using the QSTR method.

Quantitative Structure-toxicity Relationship (QSTR) models were built to evaluate the toxicity of lignocellulose-derived phenolic inhibitors on the growth of Saccharomyces cerevisiae in a bioethanol production process. The established models were proved to be reliable after rigorous validation and showed values of R2 > 0.6 and Q2LOO > 0.5. They could provide accurate guidance for alleviating the most toxic inhibitors in pretreated lignocellulosic hydrolysates, thus facilitating bioethanol production. The results showed that the inhibitors that possessed unsaturated bonds, formyl groups and carbonyl group substituents showed obvious toxicity effects. The toxicity of the inhibitors with ortho-electron-withdrawing substituents was stronger than that of metra- or para-electron-donating substituents. Ferulic acid was chosen to analyze its toxicity in practical alkali-pretreated rice straw hydrolysates because of its strong toxicity and high concentration. The results showed that its toxicity was up to 82%, which was suggested to be dominantly detoxified in the bioethanol production process.

Stimulatory effect and adsorption behavior of rhamnolipids on lignocelluloses degradation system.

Di-rhamnolipid and mixed rhamnolipid were added to rice straw degrading system to investigate their mechanism of stimulatory effect. By batch adsorption experiments, it was shown that the equilibrium adsorption time of rhamnolipids on rice straw single system was the shortest (50min). The adsorption capacity of Trichoderma reesei single system was the strongest, whose Qe,exp for di-rhamnolipid and mixed rhamnolipid was 10.57×10-2mg·g-1 and 8.13×10-2mg·g-1, respectively. The adsorption of rhamnolipids on consortia system was not the simple adduct of the two single systems. The adsorption of rhamnolipids on the three different systems might belong to chemisorptions. SEM and FTIR analyses were used to observe the morphology and to analyze the chemical functions in lignocellulosic biomass degradation with rhamnolipid. It was shown that after addition of rhamnolipids, the basic tissue in rice straw was severely destroyed and hydrogen bond was formed between biosurfactant and bacteria in lignocellulose degrading system.