Enhanced ε-Poly-L-Lysine Production in Streptomyces albulus through Multi-Omics-Guided Metabolic Engineering.

Safe and eco-friendly preservatives are crucial to preventing food spoilage and illnesses, as foodborne diseases caused by pathogens result in approximately 600 million cases of illness and 420,000 deaths annually. ε-Poly-L-lysine (ε-PL) is a novel food preservative widely used in many countries. However, its commercial application has been hindered by high costs and low production. In this study, ε-PL's biosynthetic capacity was enhanced in Streptomyces albulus WG608 through metabolic engineering guided by multi-omics techniques. Based on transcriptome and metabolome data, differentially expressed genes (fold change >2 or <0.5; p < 0.05) and differentially expressed metabolites (fold change >1.2 or <0.8) were separately subjected to gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. The integrative analysis of transcriptome, metabolome, and overexpression revealed the essential roles of isocitrate lyase, succinate dehydrogenase, flavoprotein subunit, diaminopimelate dehydrogenase, polyphosphate kinase, and polyP:AMP phosphotransferase in ε-PL biosynthesis. Subsequently, a strain with enhanced ATP supply, L-lysine supply, and ε-PL synthetase expression was constructed to improve its production. Finally, the resulting strain, S. albulus WME10, achieved an ε-PL production rate of 77.16 g/L in a 5 L bioreactor, which is the highest reported ε-PL production to date. These results suggest that the integrative analysis of the transcriptome and metabolome can facilitate the identification of key pathways and genetic elements affecting ε-PL synthesis, guiding further metabolic engineering and thus significantly enhancing ε-PL production. The method presented in this study could be applicable to other valuable natural antibacterial agents.

Combinatorial strain improvement and bioprocess development for efficient production of ε-poly-L-lysine in Streptomyces albulus.

ε-Poly-L-lysine (ε-PL) is an amino acid homopolymer with diverse potential applications in the food, pharmaceutical and cosmetic industries. To improve its biomanufacturing efficiency, strain engineering and bioprocess optimization were combined in this study. Firstly, a cocktail strain breeding strategy was employed to generate a ε-PL high-production mutant, Streptomyces albulus GS114, with enhanced L-lysine uptake capability. Subsequently, the L-lysine feeding conditions during fed-batch fermentation were systematically optimized to improve the L-lysine supply, resulting in ε-PL production reaching 73.1 ± 1.4 g/L in 5 L bioreactor. Finally, an engineered strain, S. albulus L2, with enhanced uptake capability and polymerization ability of L-lysine was constructed, achieving ε-PL production of 81.4 ± 5.2 g/L by fed-batch fermentation. This represents the highest reported production of ε-PL to date. This study provided an efficient production strategy for ε-PL and valuable insights into the high-value utilization of L-lysine.

Assessment tool based on fatty acid metabolic signatures for predicting the prognosis and treatment response in bladder cancer.

Background: Fatty acid metabolism (FAM) is closely connected with tumorigenesis as well as disease progression and affects the efficacy of platinum-based drugs. Exploring biomarkers related to FAM in bladder cancer (BLCA) is essential to improve cancer prognosis. Methods: High-throughput sequencing data from The Cancer Genome Atlas (TCGA) were bioinformatically resolved to identify molecular subtypes of fatty acid metabolic profiles in BLCA using coherent clustering analysis. Based on fatty acid metabolic profile, a prognostic model was created using COX and LASSO COX models. CIBERSORT, Estimation of STromal and Immune cells in MAlignant Tumours using Expression (ESTIMATE), MCP-Count, and single sample gene set enrichment analysis (ssGSEA) were used to assess the differences in tumor microenvironment (TME) among different molecular subtypes, prognostic groups. Kaplan-Meier (K-M) survival curve was plotted to assess patients' prognosis. Receiver operating characteristic curve (ROC) and the clinical prognostic value of prognostic models was evaluated by the Nomogram. Results: Three molecular subtypes (FAMC1, FAMC2, FAMC3) of fatty acid metabolic patterns were determined. FAMC1 showed significant prognostic advantage with immunoreactivity. Five key prognostic FAMGs were identified and RiskScore was developed. We found that patients with low RiskScore showed significantly better immune microenvironment status, survival and response to immunotherapy. Similarly, both Nomogram and RiskScore demonstrated excellent prognostic value. Conclusions: In conclusion, our study showed that the RiskScore was closely related to the clinical traits of BLCA patients. The RiskScore may provide essential clinical guidance for predicting prognosis and treatment response in bladder cancer.

SNORC knockdown alleviates inflammation, autophagy defect and matrix degradation of chondrocytes in osteoarthritis development.

Excessive inflammation and autophagy defect of chondrocytes play important roles in the pathological process of osteoarthritis (OA). The present study aimed to clarify the roles of small novel rich in cartilage (SNORC) in these pathological changes of chondrocytes in OA. Bioinformatics analysis of GEO dataset GSE207881 displayed that SNORC was a potential biomarker for OA. As confirmed by quantitative real-time PCR, immunohistochemical staining and western blotting, SNORC was significantly up-regulated in cartilage of OA rat model and interleukin (IL)-1ß-stimulated primary rat articular chondrocytes in contrast to their corresponding normal control. Knocking down SNORC in IL-1ß-induced chondrocytes obviously suppressed the production of nitric oxide (NO), IL-6, tumor necrosis factor (TNF)-α and prostaglandin E2 (PGE2) to alleviate inflammation, and reduced the protein levels of a disintegrin and metalloproteinase with thrombospondin 5 (ADAMTS5) and matrix metallopeptidase (MMP)13 and elevated collagen type 2 alpha 1 (COL2A1) level to improve matrix degradation. Down-regulation of SNORC increased Beclin1 expression and LC3II/LC3I ratio, but suppressed p62 expression to restore impaired autophagy in IL-1ß-induced chondrocytes. Moreover, down-regulating SNORC mitigated mitochondrial dysfunction and apoptosis in IL-1ß-stimulated chondrocytes. Mechanically, SNORC simultaneously activated the phosphatidylinositol-3-kinase/serine threonine kinase (PI3K/AKT) and c-Jun N-terminal kinase (JNK)/c-Jun signaling pathway in the IL-1ß-induced chondrocyte, while re-activating the PI3K and JNK signals abolished the suppressive effect of down-regulating SNORC on IL-1ß-induced chondrocyte damage. In a word, SNORC knockdown alleviates inflammation, matrix degradation, autophagy defect and excessive apoptosis of chondrocytes during OA development via suppressing the PI3K and JNK signaling pathway.

Comparison of tyrosine kinase inhibitors in the treatment of metastatic renal cell carcinoma with rhabdoid and sarcomatoid differentiations.

OBJECTIVE: To investigate the efficacy of tyrosine kinase inhibitors (TKIs) in the treatment of metastatic renal cell carcinoma (mRCC) with rhabdoid (mRCC-R) and sarcomatoid (mRCC-S) differentiations. MATERIALS AND METHODS: In this single-institutional cohort study, we included patients with RCC with rhabdoid (RCC-R) and sarcomatoid (RCC-S) differentiation, who were treated with TKIs after metastasis at our institute from 2013 to 2021. Patient characteristics, treatments, and clinical outcomes were recorded and analyzed. RESULTS: We identified 111 patients with RCC-R or RCC-S differentiations, of which 23 patients were included in the final analysis. Of the 23 patients, 10 (43.5%) were grouped as mRCC-R and 13 (56.5%) as mRCC-S. At a median follow-up of 40 months, mRCC-R and mRCC-S progressed in 7 of 10 and 12 of 13 patients, respectively. In addition, four and eight patients died in the mRCC-R and mRCC-S groups, respectively. The median progression-free survival (PFS) of the two groups was 19 months (mRCC-R: 95% confidence interval [CI] 4.08-33.92) and 7 months (mRCC-S: 95% CI 2.03-11.96), while the median overall survival (OS) was 32 months and 21 months, respectively. mRCC-S had a worse prognosis than mRCC-R. Based on the univariate Cox regression model, single metastasis or multiple metastasis of tumor, rhabdoid differentiation, and sarcomatoid differentiation were predictors of PFS but not OS. CONCLUSION: The efficacy of TKIs in the treatment of mRCC-R and mRCC-S may be different.

Integrative transcriptome and proteome revealed high-yielding mechanisms of epsilon-poly-L-lysine by Streptomyces albulus.

Introduction: ε-poly-L-lysine (ε-PL) is a high value, widely used natural antimicrobial peptide additive for foods and cosmetic products that is mainly produced by Streptomyces albulus. In previous work, we developed the high-yield industrial strain S. albulus WG-608 through successive rounds of engineering. Methods: Here, we use integrated physiological, transcriptomic, and proteomics association analysis to resolve the complex mechanisms underlying high ε-PL production by comparing WG-608 with the progenitor strain M-Z18. Results: Our results show that key genes in the glycolysis, pentose phosphate pathway, glyoxylate pathway, oxidative phosphorylation, and L-lysine biosynthesis pathways are differentially upregulated in WG-608, while genes in the biosynthetic pathways for fatty acids, various branched amino acids, and secondary metabolite by-products are downregulated. This regulatory pattern results in the introduction of more carbon atoms into L-lysine biosynthesis and ε-PL production. In addition, significant changes in the regulation of DNA replication, transcription, and translation, two component systems, and quorum sensing may facilitate the adaptability to environmental pressure and the biosynthesis of ε-PL. Overexpression of ppk gene and addition of polyP6 further enhanced the ε-PL production. Discussion: This study enables comprehensive understanding of the biosynthetic mechanisms of ε-PL in S. albulus WG-608, while providing some genetic modification and fermentation strategies to further improve the ε-PL production.

Understanding the Streptomyces albulus response to low-pH stress at the interface of physiology and transcriptomics.

Streptomyces albulus is a well-established cell factory for ε-poly-L-lysine (ε-PL) production. It has been reported that ε-PL biosynthesis is strictly regulated by pH and that ε-PL can accumulate at approximately pH 4.0, which is outside of the general pH range for natural product production by Streptomyces species. However, how S. albulus responds to low pH is not clear. In this study, we attempted to explore the response of S. albulus to low-pH stress at the physiological and global gene transcription levels. At the physiological level, S. albulus maintained intracellular pH homeostasis at ~pH 7.5, increased the unsaturated fatty acid ratio, extended the fatty acid chain length, enhanced ATP accumulation, increased H+-ATPase activity, and accumulated the basic amino acids L-lysine and L-arginine. At the global gene transcription level, carbohydrate metabolism, oxidative phosphorylation, macromolecule protection and repair, and the acid tolerance system were found to be involved in combating low-pH stress. Finally, we preliminarily evaluated the effect of the acid tolerance system and cell membrane fatty acid synthesis on low-pH tolerance via gene manipulation. This work provides new insight into the adaptation mechanism of Streptomyces to low-pH stress and a new opportunity for constructing robust S. albulus strains for ε-PL production. KEY POINTS: • S. albulus consistently remained pH i at ~7.4 regardless of the environmental pH. • S. albulus combats low-pH stress by modulating lipid composition of cell membrane. • Overexpression of cfa in S. albulus could improve low-pH tolerance and ɛ-PL titer.

Engineering Streptomyces albulus to enhance ε-poly-L-lysine production by introducing a polyphosphate kinase-mediated ATP regeneration system.

BACKGROUND: ε-Poly-L-lysine (ε-PL) is a natural and safe food preservative that is mainly produced by filamentous and aerobic bacteria Streptomyces albulus. During ε-PL biosynthesis, a large amount of ATP is used for the polymerization of L-lysine. A shortage of intracellular ATP is one of the major factors limiting the increase in ε-PL production. In previous studies, researchers have mainly tried to increase the oxygen supply to enhance intracellular ATP levels to improve ε-PL production, which can be achieved through the use of two-stage dissolved oxygen control, oxygen carriers, heterologous expression of hemoglobin, and supplementation with auxiliary energy substrates. However, the enhancement of the intracellular ATP supply by constructing an ATP regeneration system has not yet been considered. RESULTS: In this study, a polyphosphate kinase (PPK)-mediated ATP regeneration system was developed and introduced into S. albulus to successfully improve ε-PL production. First, polyP:AMP phosphotransferase (PAP) from Acinetobacter johnsonii was selected for catalyzing the conversion of AMP into ADP through an in vivo test. Moreover, three PPKs from different microbes were compared by in vitro and in vivo studies with respect to catalytic activity and polyphosphate (polyP) preference, and PPK2Bcg from Corynebacterium glutamicum was used for catalyzing the conversion of ADP into ATP. As a result, a recombinant strain PL05 carrying coexpressed pap and ppk2Bcg for catalyzing the conversion of AMP into ATP was constructed. ε-PL production of 2.34 g/L was achieved in shake-flask fermentation, which was an increase of 21.24% compared with S. albulus WG608; intracellular ATP was also increased by 71.56%. In addition, we attempted to develop a dynamic ATP regulation route, but the result was not as expected. Finally, the conditions of polyP6 addition were optimized in batch and fed-batch fermentations, and the maximum ε-PL production of strain PL05 in a 5-L fermenter was 59.25 g/L by fed-batch fermentation, which is the highest ε-PL production reported in genetically engineered strains. CONCLUSIONS: In this study, we proposed and developed a PPK-mediated ATP regeneration system in S. albulus for the first time and significantly enhanced ε-PL production. The study provides an efficient approach to improve the production of not only ε-PL but also other ATP-driven metabolites.

Improved Production of ε-Poly-L-Lysine in Streptomyces albulus Using Genome Shuffling and Its High-Yield Mechanism Analysis.

ε-Poly-L-lysine (ε-PL), a natural food preservative, has recently gained interest and mainly produced by Streptomyces albulus. Lacking of efficient breeding methods limit ε-PL production improving, knockout byproducts and increase of main product flux strategies as a logical solution to increase yield. However, removing byproduct formation and improving main product synthesis has seen limited success due to the genetic background of ε-PL producing organism is not clear. To overcome this limitation, random mutagenesis continues to be the best way towards improving strains for ε-PL production. Recent advances in Illumina sequencing opened new avenues to understand improved strains. In this work, we used genome shuffling on strains obtained by ribosome engineering to generate a better ε-PL producing strain. The mutant strain SG-86 produced 144.7% more ε-PL than the parent strain M-Z18. Except that SG-86 displayed obvious differences in morphology and ATP compared to parent strain M-Z18. Using Illumina sequencing, we mapped the genomic changes leading to the improved phenotype. Sequencing two strains showed that the genome of the mutant strain was about 2.1 M less than that of the parent strain, including a large number of metabolic pathways, secondary metabolic gene clusters, and gene deletions. In addition, there are many SNPs (single nucleotide polymorphisms) and InDels (insertions and deletions) in the mutant strain. Based on the results of data analysis, a mechanism of ε-PL overproduction in S. albulus SG-86 was preliminarily proposed. This study is of great significance for improving the fermentation performance and providing theoretical guidance for the metabolic engineering construction of ε-PL producing strains.

Strategy for enhanced performance of silicon nanoparticle anodes for lithium-ion batteries.

The modification of silicon nanoparticles for lithium-ion battery anode materials has been a hot exploration subject in light of their excellent volume buffering performance. However, huge volume expansion leads to an unstable solid electrolyte interface (SEI) layer on the surface of the silicon anode material, resulting in short cell cycle life, which is an important factor limiting the application of silicon nanoparticles. Herein, a dual protection strategy to improve the cycling stability of commercial silicon nanoparticles is demonstrated. Specifically, the Si/s-C@TiO2 composite was produced by the hydrothermal method to achieve the embedding of commercial silicon nanoparticles in spherical carbon and the coating of the amorphous TiO2 shell on the outer surface. Buffering of silicon nanoparticle volume expansion by spherical carbon and also the stabilization of the TiO2 shell with high mechanical strength on the surface constructed a stable outer surface SEI layer of the new Si/s-C@TiO2 electrode during longer cycling. In addition, the spherical carbon and lithiated TiO2 further enhanced the electronic and ionic conductivity of the composite. Electrochemical measurements showed that the Si/s-C@TiO2 composite exhibited excellent lithium storage performance (780 mA h g-1 after 100 cycles at a current density of 0.2 A g-1 with a coulombic efficiency of 99%). Our strategy offers new ideas for the production of high stability and high-performance anode materials for lithium-ion batteries.

Association of tumor mutational burden with genomic alterations in Chinese urothelial carcinoma.

The tumor mutational burden (TMB) calculated by whole-exome sequencing (WES) is a promising biomarker for the response to immune checkpoint inhibition (ICIs) in solid tumors. However, WES is not feasible in the routine clinical setting. In addition, the characteristics of the TMB in Chinese urothelial carcinoma (UC) are unclear. The aim of this study was to demonstrate the reliability of an Acornmed 808 panel and analyze the characteristics of the TMB in Chinese UC. An Acornmed 808 panel was designed and virtually validated using UC data from the cancer genome atlas (TCGA). Comprehensive analysis of sequencing and clinical data was performed to explore the characteristics of the TMB for 143 Chinese UC patients. Compared to the TMB calculated with random 808-, 500-, and 250-gene panels, the TMB calculated with the Acornmed 808 panel was closer to that calculated by WES. There were marked disparities in the mutational landscape and TMB between Chinese and TCGA UC data. The TMB was negatively associated with copy number variation (CNV). In contrast, the TMB was positive correlation with numbers of mutated DDR genes. Exposure to aristolochic acid signature was observed only in the TMB-high groups. The Acornmed 808 panel is a clinically practical method to assess the TMB. The TMB was associated with the DDR gene status and CNV counts and might be a biomarker for further stratification of UC patients. The study suggested that patients with high TMB may have a unique carcinogenic mechanism.

Epsilon-poly-L-lysine: Recent Advances in Biomanufacturing and Applications.

ε-poly-L-lysine (ε-PL) is a naturally occurring poly(amino acid) of varying polymerization degree, which possesses excellent antimicrobial activity and has been widely used in food and pharmaceutical industries. To provide new perspectives from recent advances, this review compares several conventional and advanced strategies for the discovery of wild strains and development of high-producing strains, including isolation and culture-based traditional methods as well as genome mining and directed evolution. We also summarize process engineering approaches for improving production, including optimization of environmental conditions and utilization of industrial waste. Then, efficient downstream purification methods are described, including their drawbacks, followed by the brief introductions of proposed antimicrobial mechanisms of ε-PL and its recent applications. Finally, we discuss persistent challenges and future perspectives for the commercialization of ε-PL.

Sleep and Activity Patterns Are Altered During Early Critical Illness in Mechanically Ventilated Adults.

BACKGROUND: Mechanically ventilated (MV) patients in the intensive care unit (ICU) often experience disturbed sleep and profound inactivity. OBJECTIVES: The aim of this study was to report 5 consecutive days' descriptive analyses on sleep efficiency (SE), total sleep time (TST), daytime activity ratio (DAR), and hourly activity counts among critically ill MV adults from 9 ICUs across 2 hospitals. METHODS: A secondary analysis was undertaken from our parent National Institutes of Health-funded randomized controlled trial (NIH R01 NR016702). Subjects included 31 critically ill patients from multiple ICUs. Wrist actigraphy estimated SE and TST. Mean DAR, an indicator of altered sleep-wake cycles, was calculated. Continuous 24-hour activity counts over 5 consecutive days were summarized. Descriptive analyses were used. RESULTS: A total of 31 subjects with complete actigraphy data were included. Mean age was 59.6 (SD, 17.3) years; 41.9% were male; 83.9% were White, and 67.7% were Hispanic/Latino; and the mean APACHE III (Acute Physiology and Chronic Health Evaluation III) severity of illness score was 74.5 (SD, 25.5). The mean nighttime SE and TST over the 5-day ICU period were 83.1% (SD, 16.14%) and 6.6 (SD, 1.3) hours, respectively. The mean DAR over the 5-day ICU period was 66.5% (SD, 19.2%). The DAR surpassed 80% on only 17.5% of subject days. The majority of subjects' activity level was low, falling below 1000 activity counts per hour. CONCLUSION: Our study revealed poor rest-activity cycle consolidation among critically ill MV patients during the early ICU period. Future interventional studies should promote quality sleep at nighttime and promote mobilization during the daytime.

Family automated voice reorientation (FAVoR) intervention for mechanically ventilated patients in the intensive care unit: Study protocol for a randomized controlled trial.

Delirium in the intensive care unit (ICU) affects up to 80% of critically ill, mechanically ventilated (MV) adults. Delirium is associated with substantial negative outcomes, including increased hospital complications and long-term effects on cognition and health status in ICU survivors. The purpose of this randomized controlled trial is to test the effectiveness of a Family Automated Voice Reorientation (FAVoR) intervention on delirium among critically ill MV patients. The FAVoR intervention uses scripted audio messages, which are recorded by the patient's family and played at hourly intervals during daytime hours. This ongoing orientation to the ICU environment through recorded messages in a voice familiar to the patient may enable the patient to more accurately interpret the environment and thus reduce risk of delirium. The study's primary aim is to test the effect of the FAVoR intervention on delirium in critically ill MV adults in the ICU. The secondary aims are to explore: (1) if the effect of FAVoR on delirium is mediated by sleep, (2) if selected biobehavioral factors moderate the effects of FAVoR on delirium, and (3) the effects of FAVoR on short-term and long-term outcomes, including cognition and health status. Subjects (n = 178) are randomly assigned to the intervention or control group within 48 h of initial ICU admission and intubation. The intervention group receives FAVoR over a 5-day period, while the control group receives usual care. Delirium-free days, sleep and activity, cognition, patient-reported health status and sleep quality, and data regarding iatrogenic/environmental and biobehavioral factors are collected.

Up-regulation of GhPAP1A results in moderate anthocyanin accumulation and pigmentation in sub-red cotton.

Anthocyanins are a group of important secondary metabolites, functioning as colorant in plant organs as well as protective agents against several stresses. Sub-red plant (Rs) cottons, accumulating moderate level of anthocyanins in shoots, had increased photosynthesis efficiency compared to green- (GL) and red-plant (R1) cottons. The present work aimed to clarify the molecular base of anthocyanin regulation in Rs cotton. It was found that GhPAP1A was significantly up-regulated in Rs plants compared to GL cottons, but its expression level is lower than that of GhPAP1D in R1 plants. Virus induced gene silencing of GhPAP1s inhibited the red pigmentation in Rs plants. Comparative cloning revealed a 50-bp tandem repeat in the promoter of GhPAP1A in Rs cotton, which showed stronger activity to drive the expression of downstream genes in petals. Considered that the coding sequence of GhPAP1As from Rs and GL cottons had similar functions to promote anthocyanin biosynthesis in transgenic tobaccos, we attributed moderate anthocyanin accumulation in Rs cotton to increased transcription of GhPAP1A, resulted from varied promoter structure. Our works suggested GhPAP1s as useful tool to manipulate anthocyanin level and several breeding targets, including herbivore- and pathogen- resistance, high photosynthesis efficiency and colored fibers.

Identification of the Biosynthetic Gene Cluster for the anti-MRSA Lysocins through Gene Cluster Activation Using Strong Promoters of Housekeeping Genes and Production of New Analogs in Lysobacter sp. 3655.

The Gram-negative gliding bacteria Lysobacter represent a new and rich source for bioactive natural products. In an effort to discover new antibiotics, we found a cryptic biosynthetic gene cluster (BGC) in Lysobacter sp. 3655 that shared a high similarity with the putative lysocin BGC identified in silico previously from Lysobacter sp. RH2180-5. Lysocins are cyclic lipodepsipeptides with potent activity against MRSA (methicillin-resistant Staphylococcus aureus) using a novel mode of action, but the lysocin BGC had not been experimentally verified so far. Using an activity-guided screening, we isolated the main antibiotic compound and confirmed it to be lysocin E. However, the putative lysocin BGC was barely transcribed in the wild type, in which lysocins were produced only in specific conditions and in a negligible amount. To activate the putative lysocin BGC, we screened for strongly transcribed housekeeping genes in strain 3655 and found several powerful promoters. Upon engineering the promoters into the BGC, the lysocin gene transcription was significantly enhanced and the lysocin yield was markedly increased. With readily detectable lysocins production in the engineered strains, we showed that lysocin production was abolished in the gene deletion mutant and then restored in the complementary strain, even when grown in conditions that did not support the wild type for lysocin production. Moreover, the engineered strain produced multiple new lysocin congeners. The determination of the lysocin BGC and the Lysobacter promoters will facilitate the ongoing efforts for yield improvement and new antibiotic biosynthesis using synthetic biology strategies.

Mechanisms of response to pH shock in microbial fermentation.

The following review highlights pH shock, a novel environmental factor, as a tool for the improvement of fermentation production. The aim of this review is to introduce some recent original studies on the enhancement of microbial fermentation production by pH shock. Another purpose of this review is to improve the understanding of the processes that underlie physiological and genetic differences, which will facilitate future research on the improvement of fermentation production and reveal the associated molecular mechanisms. This understanding will simultaneously promote the application of this strategy to other microbial fermentation systems. Furthermore, improvement of the cellular tolerance of genetically engineered bacteria can also be a new field of research in the future to enhance fermentation production.

Extraction and purification of ε-poly-l-lysine from fermentation broth using an ethanol/ammonium sulfate aqueous two-phase system combined with ultrafiltration.

ε-Poly-l-lysine (ε-PL) serves as a natural food preservative and is manufactured mainly by extraction from microbial fermentation broth using ion-exchange chromatography. In order to develop an alternative purification strategy, an environmentally friendly alcohol/salt aqueous two-phase system (ATPS) was explored in this study for ε-PL extraction. A study of the separation of ε-PL in different alcohol/salt systems showed that ethanol/ammonium sulfate ATPS exhibited the highest ε-PL partition coefficient and recovery ratio. Based on the phase diagram, the effect of phase composition on partition, and the removal of pigment and protein, an ATPS that was composed of 20% (w/w) ethanol and 20% (w/w) ammonium sulfate, with a feedstock at pH 9.5, was developed to extract ε-PL from the fermentation broth. This achieved an ε-PL recovery ratio of 96.15% with an ε-PL purity of 40.23% after triplicate extractions. Subsequently, desalting by ultrafiltration led to a final ε-PL product of 92.39% purity and 87.72% recovery. The ethanol/ammonium sulfate ATPS provides a new possibility for ε-PL purification.

Understanding high ε-poly-L-lysine production by Streptomyces albulus using pH shock strategy in the level of transcriptomics.

ε-Poly-L-lysine (ε-PL) is a natural food preservative, which exhibits antimicrobial activity against a wide spectra of microorganisms. The production of ε-PL was significantly enhanced by pH shock in our previous study, but the underlying mechanism is poorly understood. According to transcriptional and physiological analyses in this study, the mprA/B and pepD signal transduction system was first proved to be presented and activated in Streptomyces albulus M-Z18 by pH shock, which positively regulated the transcription of ε-PL synthetase (Pls) gene and enhanced the Pls activity during fermentation. Furthermore, pH shock changed the ratio of unsaturation to saturation fatty acid in the membrane through up-regulating the transcription of fatty acid desaturase genes (SAZ_RS14940, SAZ_RS14945). In addition, pH shock also enhanced the transcription of cytochrome c oxidase (SAZ_RS15070, SAZ_RS15075), ferredoxin reductase (SAZ_RS34975) and iron sulfur protein (SAZ_RS31410) genes, and finally resulted in the improvement of cell respiratory activity. As a result, pH shock was considered to influence a wide range of proteins including regulators, fatty acid desaturase, respiratory chain component, and ATP-binding cassette transporter during fermentation. These combined influences might contribute to enhanced ε-PL productivity with pH shock.

Systematic optimization for production of the anti-MRSA antibiotics WAP-8294A in an engineered strain of Lysobacter enzymogenes.

WAP-8294A is a group of cyclic lipodepsipeptides and considered as the first-in-class new chemical entity with potent activity against methicillin-resistant Staphylococcus aureus. One of the roadblocks in developing the WAP-8294A antibiotics is the very low yield in Lysobacter. Here, we carried out a systematic investigation of the nutritional and environmental conditions in an engineered L. enzymogenes strain for the optimal production of WAP-8294A. We developed an activity-based simple method for quick screening of various factors, which enabled us to optimize the culture conditions. With the method, we were able to improve the WAP-8294A yield by 10-fold in small-scale cultures and approximately 15-fold in scale-up fermentation. Additionally, we found the ratio of WAP-8294A2 to WAP-8294A1 in the strains could be manipulated through medium optimization. The development of a practical method for yield improvement in Lysobacter will facilitate the ongoing basic research and clinical studies to develop WAP-8294A into true therapeutics.