Engineering Scheffersomyces segobiensis for palmitoleic acid-rich lipid production

Palmitoleic acid (POA; C16:1) is an essential high-value ω-7-conjugated fatty acid with beneficial bioactivities and potential applications in the nutraceutical and pharmaceutical industries. Previously, the oleaginous yeast Scheffersomyces segobiensis DSM27193 has been identified as a promising production host as an alternative for POA extraction from plant or animal sources. Here, the POA-producing capacity of this host was further expanded by optimizing the fermentation process and molecular strain engineering. Specifically, a dual fermentation strategy (O-S dynamic regulation strategy) focused on the substrate and dissolved oxygen concentration was designed to eliminate ethanol and pyruvate accumulation during fermentation. Key genes influencing POA production, such as jen, dgat, ole were identified on the transcriptional level and were subsequently over-expressed. Furthermore, the phosphoketolase (Xpk)/phosphotransacetylase (Pta) pathway was introduced to improve the yield of the precursor acetyl-CoA from glucose. The resulting cell factory SS-12 produced 7.3 g/L of POA, corresponding to an 11-fold increase compared to the wild type, presenting the highest POA titre reported using oleaginous yeast to date. An economic evaluation based on the raw materials, utilities and facility-dependent costs showed that microbial POA production using S. segobiensis can supersede the current extraction method from plant oil and marine fish. This study reports the construction of a promising cell factory and an effective microbial fermentation strategy for commercial POA production.

Microbial synthesis of pyrroloquinoline quinone

Pyrroloquinoline quinone (PQQ) is a peptide-modified natural product. PQQ has important physiological functions such as anti-oxidation, anti-aging, and immunity enhancement. However, due to the lack of in-depth understanding of PQQ biosynthesis and regulation, inefficient PQQ production level limits its wide application. Accordingly, there is still an urgent need to develop high-yielding strains for synthesis of PQQ. This paper reviewed the research and development trends on the PQQ biosynthetic pathways, catalytic reaction mechanism of key enzymes, and the selection of high-yielding strains, which also prospects for the future construction of PQQ biosynthetic microbial cell factories.

DNA-bridged double gold nanoparticles-based immunochromatography for dual-mode detection of ochratoxin A

A novel immunochromatography strip (ICS) based on the DNA-bridged double gold nanoparticles was established and evaluated for the dual-mode detection of ochratoxin A (OTA). For this purpose, the streptavidin was coupled with the big size of gold nanoparticle (40 nm, AuNP), the OTA monoclonal antibody and biotinylated DNA-SH were simultaneously immobilized on the small size of AuNP (20 nm), and then the enhanced ICS was self-assembled and evaluated. The dual-mode detection of semi-quantification and quantification had been achieved and performed by the proposed ICS. The LOD for semi-quantification (semi-Q-LOD) was 0.06 ng/mL by the directly naked eye (eightfold enhanced than conventional ICS). By the on-site reader, the LOD for quantification (Q-LOD) was 0.03 ng/mL (threefold enhanced), with the detection range between 0.03 and 1.2 ng/mL. The specificity, reliability, and practicability had been well represented. Furthermore, the OTA-positive results of the enhanced ICS method correlated well with those obtained by the referenced HPLC-MS/MS for the market samples. This study provided a new ICS pattern of semi-quantification and quantification for OTA contamination, which could be used as a valuable reference for improving the ICS technology and enhancing the sensitivity.

Antifungal effects of amaryllidaceous alkaloids from bulbs of Lycoris spp. against Magnaporthe oryzae

BACKGROUND

Rice blast caused by Magnaporthe oryzae is one of the most devastating diseases of rice, and novel fungicides for controlling rice blast are needed owing to the problem of resistance to commonly used control agents. We previously found that methanol extract of Lycoris radiata (L'Her.) Herb. showed an excellent inhibitory effect on mycelial growth of M. oryzae, indicating its potential for developing control agents against M. oryzae. In this study, we aim to investigate the antifungal effects of different Lycoris spp. against M. oryzae, and clarify the main active components.

RESULTS

Extracts from bulbs of seven Lycoris spp. showed excellent inhibitory effects on mycelial growth and spore germination of M. oryzae at 400 mg L^-1 . Liquid chromatography-tandem mass spectrometry was employed to analyze the components of the extracts, and heatmap clustering analysis with Mass Profiler Professional software revealed that lycorine and narciclasine may be the main active components. Lycorine and narciclasine, together with three other amaryllidaceous alkaloids (AAs), were then isolated from bulbs of Lycoris spp. Antifungal assays showed that lycorine and narciclasine had good inhibitory activities against M. oryzae in vitro, but the other three AAs showed no antifungal activities under test concentrations. In addition, lycorine and the ethyl acetate part of L. radiata showed good antifungal effects against M. oryzae in vivo, but narciclasine showed phototoxicity on rice when used alone.

CONCLUSION

Extracts of test Lycoris spp. and the main active component lycorine have excellent antifungal activities against M. oryzae, and are good candidates for developing control agents against M. oryzae. © 2023 Society of Chemical Industry.

Quickly assessing disinfection effectiveness to control the spread of African swine fever virus

Infectious African swine fever virus (ASFV) can cause the spread and morbidity of African swine fever, while the inactivated virus cannot. When they are not distinguished separately, the detection results will lack authenticity and cause unnecessary panic and detection cost. The detection technology based on cell culture is complex, high-cost, and time-consuming in practice, which is not conducive to the rapid detection of infectious ASFV. In this study, a propidium monoazide (PMA) qPCR detection method for rapid diagnosis of infectious ASFV was constructed. Parameters of PMA concentration, light intensity, and lighting time were under strict safety verification and comparative analysis for optimization. The results determined that the optimal condition for PMA to pretreat ASFV was the final concentration of PMA 100 μM. The light intensity was 40 W, the light duration was 20 min, the target fragment size of the optimal primer probe was 484 bp, and its detection sensitivity for infectious ASFV was 10^1.28 HAD₅₀/mL. In addition, the method was innovatively applied to the rapid evaluation of disinfection effect. When ASFV concentration was less than 10^2.28 HAD₅₀/mL, the method could still be effective for the evaluation of thermal inactivation effect, and the evaluation ability of chlorine-containing disinfectants was better, and the applicable concentration could reach 10^5.28 HAD₅₀/mL. It is worth mentioning that this method can not only reflect whether the virus is inactivated, but also indirectly reflect the degree of damage to viral nucleic acid caused by disinfectants. In conclusion, the PMA-qPCR constructed in this study can be applied to laboratory diagnosis, disinfection effect evaluation, drug development, and other aspects of infectious ASFV and can provide new technical support for effective prevention and control of ASF. KEY POINTS: • A rapid detection method for infectious ASFV was developed • Provide a new scheme for rapid evaluation of disinfection effect of chlorine-containing disinfectants • PMA-qPCR can simultaneously show the survival status of the virus and the damage of nucleic acid.

Report of genome sequence of Rhodococcus biphenylivorans strain GA1, an isolate capable of efficiently degrading lignin and its derivates

Rhodococcus biphenylivorans GA1 was successfully isolated, which can efficiently degrade alkali lignin and a variety of lignin-derived aromatic compounds as the sole carbon source. Whole genome sequencing of strain GA1 showed that it possessed G + C content of 68% with the size of 6.0 Mb and 4319 putative open reading frames (ORFs). Four replicons consisting of one circular chromosome (ChrA1) and three circular plasmids (pGA1, pGA2, pGA3) were found. Among these annotated proteins, lignin depolymerizing peroxidases (Dyp) and two lignin-derived aromatic compounds cleavage dioxygenases, protocatechuate 3,4-dioxygenase(P34D) and catechol-1,2-dioxygenase (C12D) play key roles in the catabolism of lignin.

Seed priming and foliar application with jasmonic acid enhance salinity stress tolerance of soybean (Glycine max L.) seedlings

BACKGROUND

Jasmonic acid (JA) is an important molecule that has a regulatory effect on many physiological processes in plant growth and development under abiotic stress. This study investigated the effect of 60 μmol L-1 of JA in seed priming (P) at 15 °C in darkness for 24 h, foliar application (F), and/or their combination effect (P + F) on two soybean cultivars - 'Nannong 99-6' (salt tolerant) and 'Lee 68' (salt sensitive) - under salinity stress (100 mmol L-1 sodium chloride (NaCl)).

RESULTS

Salinity stress reduced seedling growth and biomass compared with that in the control condition. Priming and foliar application with JA and/or their combination significantly improved water potential, osmotic potential, water use efficiency, and relative water content of both cultivars under salinity stress. Similarly, seed priming with JA, foliar application of JA, and/or their combination significantly improved the following properties under salinity stress compared with the untreated seedlings: net photosynthetic rate by 68.03%, 59.85%, and 76.67% respectively; transpiration rate by 74.85%, 55.10%, and 80.26% respectively; stomatal conductance by 69.88%, 78.25%, and 26.24% respectively; intercellular carbon dioxide concentration by 61.64%, 40.06%, and 65.79% respectively; and total chlorophyll content by 47.41%, 41.02%, and 55.73% respectively. Soybean plants primed, sprayed with JA, or treated with their combination enhanced the chlorophyll fluorescence, which was damaged by salinity stress. JA treatments improved abscisic acid, gibberellic acid, and JA levels by 60.57%, 62.50% and 52.25% respectively under salt stress compared with those in the control condition. The transcriptional levels of the FeSOD, POD, CAT, and APX genes increased significantly in the NaCl-stressed seedlings irrespective of JA treatments. Moreover, JA treatment resulted in a reduction of sodium ion concentration and an increase of potassium ion concentrations in the leaf and root of both cultivars regardless of salinity stress. Monodehydroascorbate reductase, dehydroascorbate reductase, and proline contents decreased in the seedlings treated with JA under salinity stress, whereas the ascorbate content increased with JA treatment combined with NaCl stress.

CONCLUSION

The application of 60 μmol L-1 JA improved plant growth by regulating the interaction between plant hormones and hydrogen peroxide, which may be involved in auxin signaling and stomatal closure under salt stress. These methods could efficiently protect early seedlings and alleviate salt stress damage and provide possibilities for use in improving soybean growth and inducing tolerance against excessive soil salinity. © 2020 Society of Chemical Industry.

Evaluation of the effects of different stocking densities on the sediment microbial community of juvenile hybrid grouper (♀Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus) in recirculating aquaculture systems

Aquatic microorganisms are an important part of aquatic ecosystems because they are involved in nutrient cycling and water quality, eventually influencing fish productivity. However, at present, reports on the effect of stocking density on microorganisms in sediment samples in recirculating aquaculture systems (RAS) are relatively rare. In this study, the changes in the microbial community in an RAS were investigated under different stocking densities of juvenile hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus). Total DNA was extracted from the sediment samples, the 16S rDNA gene was amplified, and the bacterial community was analysed by Illumina high-throughput sequencing. We identified 741 OTUs from a total of 409,031 reads. Based on the analysis of bacterial composition, richness, diversity, bacterial 16S and rDNA gene abundance; sediment sample comparisons; and the existence of specific bacterial taxa within four densities, we concluded that the dominant phyla in all samples were similar and included: Proteobacteria, Bacteroidetes, Nitrospirae, Planctomycetes, Verrucomicrobia, and Chloroflexi. However, their relative distributions differed at different fish densities. Linear discriminant analysis further indicated that the stocking treatment influenced the sediment bacterial community. This study indicates that under RAS aquaculture, mode density is a factor regulating the microbial community, which provides insights into microbe management in RAS culture.