2,3,5,6-Tetramethylpyrazine (TMP) is an active pharmaceutical ingredient originally isolated from Ligusticum wallichii for curing cardiovascular and cerebrovascular diseases and is widely used as a popular flavoring additive in the food industry. Hence, there is a great interest in developing new strategies to produce this high-value compound in an ecological and economical way. Herein, a cost-competitive combinational approach was proposed to accomplish green and high-efficiency production of TMP. First, microbial cell factories were constructed to produce acetoin (3-hydroxy-2-butanone, AC), an endogenous precursor of TMP, by introducing a biosynthesis pathway coupled with an intracellular NAD⁺ regeneration system to the wild-type Escherichia coli. To further improve the production of (R)-AC, the metabolic pathways of by-products were impaired or blocked stepwise by gene manipulation, resulting in 40.84 g/L (R)-AC with a high optical purity of 99.42% in shake flasks. Thereafter, an optimal strain designated GXASR11 was used to convert the hydrolysates of inexpensive feedstocks into (R)-AC and achieved a titer of 86.04 g/L within 48 h in a 5-L fermenter under optimized fermentation conditions. To the best of our knowledge, this is the highest (R)-AC production with high optical purity (≥98%) produced from non-food raw materials using recombinant E. coli. The supernatant of fermentation broth was mixed with diammonium phosphate (DAP) to make a total volume of 20 ml and transferred to a high-pressure microreactor. Finally, 56.72 g/L TMP was obtained in 3 h via the condensation reaction with a high conversion rate (85.30%) under optimal reaction conditions. These results demonstrated a green and sustainable approach to efficiently produce high-valued TMP, which realized value addition of low-cost renewables.

Acetoin is an important four-carbon platform chemical with versatile applications. Optically pure (R)-acetoin is more valuable than the racemate as it can be applied in the asymmetric synthesis of optically active α-hydroxy ketone derivatives, pharmaceuticals, and liquid crystal composites. As a cytotoxic solvent, acetoin at high concentrations severely limits culture performance and impedes the acetoin yield of cell factories. In this study, putative genes that may improve the resistance to acetoin for Escherichia coli were screened. To obtain a high-producing strain, the identified acetoin-resistance gene was overexpressed, and the synthetic pathway of (R)-acetoin was strengthened by optimizing the copy number of the key genes. The engineered E. coli strain GXASR-49RSF produced 81.62 g/L (R)-acetoin with an enantiomeric purity of 96.5% in the fed-batch fermentation using non-food raw materials in a 3-L fermenter. Combining the systematic approach developed in this study with the use of low-cost feedstock showed great potential for (R)-acetoin production via this cost-effective biotechnological process.

Long-term sugarcane monoculture triggers severe continuous cropping obstacles accompanied by notable soil microecological degradation, including nutrient immobilization, soil acidification, salinization and microbial community imbalance. Physical soil remediation via industrial microwave irradiation represents a promising approach to alleviate soil degradation. Nevertheless, the interactive variations in soil structure, fertility and microbial communities under gradient 915 MHz industrial microwave irradiation remain poorly understood. This study aimed to clarify the correlations among physicochemical properties, microbial structure and functional genes of sugarcane continuous cropping soil under microwave thermal regulation. A continuous 915 MHz microwave device with power gradients (0, 2, 4, 6, 8 kW) and a fixed irradiation duration of 10 min was adopted. Soil samples were incubated for 0, 15 and 30 weeks for comprehensive parameter determination. The results demonstrated that appropriate microwave power exerted positive regulatory effects on soil thermal intensity, aggregate disruption and microbial succession. Soil organic matter (SOM) and pH were key factors modulating the distribution of beneficial and pathogenic microorganisms. The 4 kW treatment disintegrated compact soil aggregates, activated mineral-bound nutrients, relieved soil acidification and salinization, and upregulated genes responsible for nutrient mineralization and antifungal metabolism to sustain high abundances of partial biocontrol fungi. In contrast, high-power treatments (6 kW and 8 kW) induced substantial early-stage SOM loss, reduced soil pH and aggravated salinization in the late incubation stage, thereby inhibiting symbiotic beneficial fungi. Collectively, 4 kW was the optimal microwave parameter in this study to coordinate soil structural, nutritional and microecological balance. This study provides a theoretical basis and technical guidance for the green remediation of soil plagued by sugarcane continuous cropping obstacles.

Huanglongbing (HLB), associated with Candidatus Liberibacter asiaticus (CLas), has severely impacted global citrus production, with no economically viable control measures currently available. This study explored microwave treatment at 2450 MHz as an innovative physical method for HLB control, combining pathogen elimination efficacy with metabolomic analysis. In controlled experiments, 36 HLB-infected citrus plants were treated with 500 W or 250 W microwave irradiation and underwent 10 cycles, achieving up to 99.83% reduction CLas titer. Non-targeted metabolomic analysis identified 15 significantly altered metabolites, including upregulated beta-caryophyllene and lysophosphatidylinositols, and downregulated 5′-S-methyl-5′-thioadenosine. The results indicate that microwave treatment effectively suppressed CLas while simultaneously triggering citrus physiological metabolic changes. These findings suggest that microwave treatment could serve as a sustainable alternative to chemical controls. However, further optimization of parameters, such as wavelengths, voltages, currents, and safety protocols, will be essential for practical field implementation.

Conventional hot-air drying (HDT) can hardly degrade pesticide residues in jasmine tea effectively, and chemical methods tend to cause secondary pollution, which seriously endangers human health and restricts the sustainable development of the tea industry. To address this issue, this study systematically investigated the effects of four green physical pretreatments (ultrasonic, microwave, high-energy electron beam, and ultraviolet irradiation) combined with HDT on pesticide residues, color parameters, main chemical components, and volatile flavor compounds of jasmine tea. The results showed that all pretreatments altered the color of both dry tea leaves and tea infusions and significantly reduced pesticide residues. Among them, microwave pretreatment (MDT) exhibited the optimal degradation performance, with a total degradation rate of 68.99% for six pesticides, and significantly increased the contents of chemical components such as free amino acids and tea polysaccharides. GC-MS analysis revealed that different pretreatments exerted significant impacts on the aroma profile of jasmine tea. Among the key aroma components, the relative content of trans-linalool oxide (furanoid) increased significantly following MDT and HEDT treatments, and all four pretreatments produced significant effects on the levels of methyl salicylate. This study demonstrates that physical pretreatments can achieve both pesticide residue reduction and flavor quality improvement of jasmine tea, providing a practical technical reference for the industrial processing and quality control of jasmine tea.