WRKY transcription factors, one of the largest families of transcriptional regulators in plants, play important roles in plant development and various stress responses. The WRKYs of Caragana intermedia are still not well characterized, although many WRKYs have been identified in various plant species. We identified 53 CiWRKY genes from C. intermedia transcriptome data, 28 of which exhibited complete open reading frames (ORFs). These CiWRKYs were divided into three groups via phylogenetic analysis according to their WRKY domains and zinc finger motifs. Conserved domain analysis showed that the CiWRKY proteins contain a highly conserved WRKYGQK motif and two variant motifs (WRKYGKK and WKKYEEK). The subcellular localization of CiWRKY26 and CiWRKY28–1 indicated that these two proteins localized exclusively to nuclei, supporting their role as transcription factors. The expression patterns of the 28 CiWRKYs with complete ORFs were examined through quantitative real-time PCR (qRT-PCR) in various tissues and under different abiotic stresses (drought, cold, salt, high-pH and abscisic acid (ABA)). The results showed that each CiWRKY responded to at least one stress treatment. Furthermore, overexpression of CiWRKY75–1 and CiWRKY40–4 in Arabidopsis thaliana suppressed the drought stress tolerance of the plants and delayed leaf senescence, respectively. Fifty-three CiWRKY genes from the C. intermedia transcriptome were identified and divided into three groups via phylogenetic analysis. The expression patterns of the 28 CiWRKYs under different abiotic stresses suggested that each CiWRKY responded to at least one stress treatment. Overexpression of CiWRKY75–1 and CiWRKY40–4 suppressed the drought stress tolerance of Arabidopsis and delayed leaf senescence, respectively. These results provide a basis for the molecular mechanism through which CiWRKYs mediate stress tolerance.

Fermented porridge is usually made though the process of natural fermentation of grains with higher starch. Organic acids are the main flavor compounds in fermented porridge. However, the understanding of the correlation between the microbial communities and organic acids is limited in the fermentation process of traditional Chinese sour porridge (CSP). In this study, the dynamic of bacterial community and organic acids was investigated and the correlation between bacterial communities and organic acids was revealed during the fermentation process of CSP. The results showed that the richness and diversity of the bacterial communities at initial state (0h) were significantly higher than other period and the concentration of 9 organic acids (oxalic acid, tartaric acid, malic acid, lactic acid, acetic acid, citric acid, and succinic acid) increased with the fermentation process. Pediococcus and Lactobacillus were the dominative genus in the fermentation process of CSP and the fermentation process of CSP can be divided into three stages, with 0 h as the initial stage, 6–18 h as the second group and 24–36 h as the third based on PCA and cluster analysis. Moreover, 20 bacteria genus had significant correlation with (|ρ|>0.7) organic acids based on O2PLS analysis and The Lactobacillus and Acinetobacter were positively correlated with seven (succinic acid, tartaric acid, lactic acid, oxalic acid, acetic acid, malic acid and succinic acid) and four (tartaric acid, acetic acid, lactic acid, and α-ketoglutarate) organic acids respectively. Clostridium, Paenibacillus, Cupriavidus, Shinella, Streptococcus, Flavobacterium, Enterobacteriaceae, Cyanobacteria, Pseudomonas, Ralstonia, Microbacterium, Bradyrhizobiaceae, Escherichia-Shigella, Acidovorax, Leuconostoc, Alphaproteobacteria, Pediococcus, and Mitochondria were negatively correlated with organic acids in the fermentation process of CSP.

2-Keto-l-gulonic acid (the precursor of vitamin C) is bio-converted from l-sorbose by mixed fermentation of Ketogulonicigenium vulgare and a helper strain. The helper strain promotes the conversion of 2-KLG by enhancing the growth of K. vulgare, but its growth is greatly inhibited by high concentration of l-sorbose, which consequently influence the 2-KLG production. The aim of this study is to obtain l-sorbose-tolerant helper strain (LHS) by experimental evolution for reduced l-sorbose-inhibition-effect and enhanced 2-KLG productivity in high concentration of l-sorbose. After three steps screening by using our devised screening strategy, three strains (i.e., Bc 21, Bc 47, Bc 50) with high resistance to high concentration of l-sorbose were obtained. The fermentation tests by co-culturing Bc 21 and K. vulgare 418 showed that the production of 2-KLG was increased by 17.9% in 11% l-sorbose medium than that in 8% after 55 h of fermentation and the conversion rate was 89.5%. The results suggested that Bc 21 could be an ideal helper strain for 2-KLG production under high concentration of l-sorbose and demonstrated the feasibility of using experimental evolution to breed LHS for vitamin C production.

Fungal spoilage of food is a worldwide concern prompting the development of many antimicrobial agents and applications. In this study, the cell-free supernatant (CFS) of Lacticaseibacillus paracasei ALAC-4 had a significant inhibition effect on fungi. The CFS with antifungal activities were combined with chitosan (CS) matrix to prepare an active packaging CS-CFS films by using a solvent casting method and used for the packaging of Mongolian cheese for 15 days during storage at 4 ± 1℃. The optimized formulation of the film were 1.25% (w/v) chitosan, 1.75% (w/v) gelatin, 0.3% (v/v) glycerol, and 9.6% (w/v) CFS. It was found that CS-CFS films exhibited strong antifungal activities against molds and yeasts, especially Candida albicans, and also had excellent mechanical properties. Additionally, FTIR spectroscopy indicated that hydrogen bonds between the CFS and CS formed, and there was a smooth surface, compact cross-section observed in SEM morphologies of CS-CFS films. Furthermore, CS-CFS film also displayed a strong antifungal effect against molds and yeasts on cheese surface. These results suggest that the chitosan-based CS-CFS film has a promising application for Mongolian cheese and food preservation.

As a key precursor of vitamin C, 2-keto-L-gulonic acid (2-KLG) was mainly produced from L-sorbose by mixed fermentation of Ketogulonicigenium vulgare and a helper strain (Bacillus spp.) with a low conversion rate for decades. The aim of this study was to enhance the 2-KLG production by co-culturing K. vulgare and Bacillus megaterium using three-stage temperature control (TSTC) strategy. By investigating the temperature effect on the 2-KLG fermentation, the optimum temperatures for the growths of K. vulgare and B. megaterium were 32 °C and 29 °C, respectively, while the optimum temperature for 2-KLG production was 35 °C. We developed a TSTC process: the temperature was kept at 32 °C during the first 16 h of fermentation, then decreased to 29 °C for the following 14 h, and maintained at 35 °C to the end of fermentation. By using this new process, the productivity and yield of 2-KLG from L-sorbose were obtained at 2.19 ± 0.19 g/L/h and 92.91 ± 1.02 g/L in 20-L fermentors for 5 batches, respectively, which were 22.35% and 6.02% higher than that of the control treatment (the single temperature of 29 °C). The increased cell density of K. vulgare during the exponential phase and the enhanced SDH activity (increased by 25.18% at 36 h, 17.14% at 44 h) in the production stage might be the reasons for enhanced 2-KLG conversion rate and yield. Our results demonstrated the feasibility of the TSTC strategy for 2-KLG production.