Understanding microbial spoilage dynamics is critical for ensuring the safety and extending the shelf life of vacuum-packed meat. This study integrated 16S ribosomal ribonucleic acid (rRNA) high-throughput sequencing with visible-near-infrared (Vis-NIR, 400-1000 nm) hyperspectral imaging to non-destructively monitor the progression of microbial spoilage in vacuum-packed lamb during refrigerated storage. Microbial succession followed a three-phase trajectory, beginning with Pseudomonas dominance (99.41% at day 0), followed by a midstage proliferation of Carnobacterium (61.99% at day 8), and culminating in the late-stage predominance of unclassified Enterobacteriaceae (84.16% at day 12), driven by anaerobic adaptation. Spectral analysis revealed dynamic changes associated with microbial activity. The increase in reflectance in the 400-900 nm range was influenced by multiple factors, including microbial extracellular polymeric substances (EPS), changes in tissue water distribution, and early structural alterations in proteins and lipids. A sharp decline in the 900-1000 nm region was observed concurrently, associated with proteolytic tissue degradation. Key spectral biomarkers, such as absorption valleys at 540 and 566 nm (oxymyoglobin degradation) and peaks near 720 nm (lipid oxidation), corresponded with specific microbial transitions and were supported by hierarchical clustering. A particle swarm optimization-enhanced extreme learning machine (ELM + PSO) model achieved 97.5% accuracy in classifying storage days based on these spectral features, outperforming K-nearest neighbor (KNN, 92.5%) and partial least squares-discriminant analysis (PLS-DA, 85.0%). The Shannon diversity index (1.22-1.57) showed a strong temporal correlation with spectral variation, although causal relationships warrant further co-localized studies. An optimized spectral preprocessing pipeline combining Savitzky-Golay filtering, wavelet denoising, and spatial smoothing significantly enhanced data discriminability. This study establishes a robust framework linking microbial ecology to spectral analytics, offering an intelligent solution for real-time, non-invasive quality control in meat preservation systems.
The role of nicotinamide (NAM) in maintaining postharvest quality, regulating respiratory and energy metabolism, and preserving redox-related metabolism was investigated in Lingwu long jujube fruit. NAM treatment maintained fruit quality during storage, as shown by improved color retention, reduced weight loss, higher firmness, lower relative electrical conductivity, and better retention of total soluble solids, titratable acidity, total sugars, and vitamin C. NAM also increased total phenolics and flavonoids and slowed the changes in volatile flavor compounds, thereby maintaining flavor characteristics closer to those of fresh fruit. Transcriptomic analysis indicated that NAM regulated genes associated with carbohydrate metabolism, redox processes, secondary metabolism, membrane transport, and stress responses. Biochemical analyses further showed that NAM weakened glycolytic activity but enhanced the pentose phosphate pathway, as indicated by reduced activities of hexokinase, phosphofructokinase, pyruvate kinase and phosphoglucose isomerase and increased activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Moreover, NAM preserved mitochondrial integrity and increased succinate dehydrogenase, cytochrome c oxidase, H+-ATPase and Ca2+-ATPase activities, which contributed to higher ATP levels and improved energy status. Moreover, NAM regulated pyridine nucleotide metabolism by enhancing NADK activity and promoting NADPH accumulation, which may strengthen cellular reducing power. Overall, NAM delayed postharvest senescence in Lingwu long jujube fruit by coordinating respiratory metabolism, mitochondrial energy supply, and redox-related metabolism. These findings provide a potential strategy for improving postharvest preservation and maintaining the commercial quality of Lingwu long jujube fruit.
Although considerable advances have been made in directly converting ethanol to butadiene (ETB), the catalyst deactivation mechanism remains incompletely understood. Herein, ZnZr/Si-beta catalyst was chosen as a model catalyst to elucidate the carbon deposition induced deactivation mechanism. The comprehensive characterization revealed that the primary cause of deactivation is the accumulation of coke deposits on the catalyst surface or within the pores. The significant accumulation of acetaldehyde results from inhibited aldol condensation, caused by carbon deposits covering the active sites. The accumulated acetaldehyde undergoes aldol condensation to form acetone. Subsequently, the generated acetone and acetaldehyde participate in self- and cross-condensation reaction, generating long-chain unsaturated aldehydes and ketones. Subsequent cyclization reaction of these compounds generates complex compounds such as 2,4-dimethylbenzaldehyde, dibenzofuran, and fluorene, which ultimately poison the catalyst by blocking its active sites. These insights offer valuable theoretical guidance for designing novel catalysts for the direct ethanol-to-butadiene conversion.
Fruit softening is a critical determinant of apple fruit texture and postharvest quality; however, the transcriptional mechanisms controlling cell wall remodeling during this process remain largely unknown. Previous studies have shown that an A/T allelic variation at nucleotide position 517 of the transcription factor MdNAC5 is significantly associated with natural variation in fruit firmness. Based on this finding, the present study integrated ChIP-seq and transcriptome data from MdNAC5 transgenic materials to identify an expansin gene, MdEXPA8, involved in cell wall remodeling. Yeast one-hybrid, dual-luciferase reporter, and electrophoretic mobility shift assays demonstrated that MdEXPA8 is a direct downstream target of MdNAC5, and that the MdNAC5A allele exhibits a significantly stronger transcriptional activation of MdEXPA8 than MdNAC5T. Consistently, the contents of cell wall components were significantly lower in MdNAC5A transgenic lines than in MdNAC5T lines. Further homologous and heterologous expression analyses in apple and tomato revealed that overexpression of MdEXPA8 markedly accelerated cell wall disassembly, reduced fruit firmness, and promoted fruit softening. Spatiotemporal expression analysis showed that MdEXPA8 expression gradually increased during fruit development and ripening, was significantly negatively correlated with fruit firmness, and was higher in cultivars exhibiting faster softening. Collectively, these results demonstrate that allelic variation in MdNAC5 regulates apple fruit softening through allele-dependent transcriptional activation of MdEXPA8, providing an important candidate gene for improving fruit texture.
Petcoke (PC) steam gasification for hydrogen production using biomass ash as cheap-effective catalyst was promising. KCl, CaCO3 and SiO2 were used to establish biomass ash model system (BAMS). Influence of BAMS on char structure evolution during PC gasification and synergistic effects among BAMS components were investigated. Furthermore, synergistic effect mechanism of BAMS was revealed. The results indicate that interactions among BAMS components led to synergistic effects with three types: synergistic enhancement of catalytic effect (K-Ca>K-Ca-Si), synergistic inhibition of catalytic effect (K-Si), and synergistic enhancement of inhibitory effect (Ca-Si). Synergistic effects initially increased and then decreased as reaction proceeded. Influence of BAMS component combinations on the semi-char carbon structure and content of C-C functional groups exhibited similar phenomena. KCl and CaCO3 synergistically enhanced destruction of carbon structure, while SiO2 weakened catalytic effects of K and Ca through fixation reactions. Preferential combination of CaCO3 and SiO2 led to catalytic activity remaining of KCl.
