Bioresource Technology最新文献

The present study investigates the natural ability of Bacillus velezensis R22 to produce 2,3-BD from two inulin-rich substrates - insoluble and soluble chicory flour. After complex optimization of the media content and process parameters by consecutive application of Plackett-Burman design and response surface methodology, the strain R22 was capable of producing 71.2 g/L (95.5 % R,R-2,3-BD) and 96.4 g/L 2,3-BD (86.2 % R,R-2,3-BD) from insoluble and soluble chicory flour without preliminary hydrolysis. The optimal conditions were: K₂HPO₄ concentration of 3.43 g/L, pH 6.68, and agitation speed of 363 rpm. The total inulinase activity of R22 ranged between 85 and 94 U/mL and was provided by the synergistic action of two enzymes: cytoplasmic SacC and membrane-located LevB, which were purified and characterized. The ability to directly convert inulin, its non-pathogenic nature, and the formation of predominantly R,R-2,3-BD singled out B. velezensis R22 as a new promising industrial producer of 2,3-BD from inulin-rich plant biomass.

CO₂/CH₄ separation is crucial for biogas upgrading. In this study, the bamboo-derived activated carbons (BACs) were prepared with different ratios of potassium hydroxide (KOH)/bamboo charcoal (BC), and the hybrid sorbents of aqueous BACs were developed for CO₂/CH₄ separation. Both the gas solubility and sorption rate were measured, and Henry's constant and liquid-side mass-transfer coefficient as well as the CO₂/CH₄ selectivity were calculated. Meanwhile, the comprehensive performances of aqueous BACs were evaluated using a novel index, and the cost of biogas upgrading using the aqueous BACs was estimated and compared to the commercialized technology. The results proved the effectiveness of aqueous BACs, and the comprehensive performance of 7.0 wt% aqueous BAC with the KOH/BC mass ratio of 2:1 was 4.2 times than that of H₂O, having the potential to decrease the average CO₂/CH₄ separation cost by 65.0% compared to the commercialized technology.

Dynamic oxygen fluctuations in activated sludge were investigated to enhance valuable biochemical production during wastewater treatment. Batch experiments compared constant aeration with rapid cycling between oxygen-rich and oxygen-poor states. Fluctuating oxygen concentrations (0-2 mg/L) significantly increased production of valuable biochemicals compared to constant oxygen concentration (2 mg/L). Continuous oxygen perturbations increased free amino acids by 35.7 ± 7.6 % and free fatty acids by 76.4 ± 13.0 %, while intermittent perturbations with anoxic periods enhanced free amino acids by 42.4 ± 8.1 % and free fatty acids by 39.3 ± 7.7 %. Fourteen standard amino acids showed significant increases, and most fatty acids had carbon chain lengths between C12-C22. Mechanistically, oxygen perturbations activated FNR and ArcA regulons, resulting in lower relative abundances of TCA cycle enzymes and higher abundances of amino acid and fatty acid biosynthetic enzymes. These findings demonstrate that controlled oxygen fluctuations in wastewater treatment can enhance the biochemical value of activated sludge with minimal process modifications, facilitating resource recovery.

Background: The industrial production of L-threonine faces challenges because of high production costs, especially those of substrates, meaning new production methods are needed.

Methods: Fur, a new global transcription factor related to L-threonine biosynthesis, was discovered in this study. Multidimensional regulation combined with global transcriptional machinery engineering was used to modify an Escherichia coli strain.

Results: The most efficient mutant showed high titer (154.2 g/L), productivity (2.14 g/L/h), and yield (0.76 g/g) of L-threonine production. These three parameters indicated that these engineering strategies were economically feasible for developing high L-threonine-producing strains. We integrated the sucrose utilization gene cluster into the genome to further reduce the production cost of L-threonine. Using untreated cane molasses as the substrate, L-threonine was successfully produced with a titer of 92.46 g/L and a cost reduction of 48 %.

Conclusion: This research offers advantages for industrial scalability, and the resulting engineered bacterium holds significant industrial application potential.

Carbonic anhydrases (CAs) has garnered increasing attention in carbon capture, utilization and storage (CCUS) due to their ecological friendliness. However, most of them suffer susceptibility to deactivation in harsh conditions. Herein, a reliable dataset was adopted for creating ancestral CAs through an optimized ancestral sequence reconstruction (ASR) method. After prescreening, the ancestor AncCA19 was obtained and successfully expressed. The hydration activity of AncCA19 was as high as 58,859 WAU/mg, with the optimum temperature and pH obtained by esterase assay at 100 ℃ and 9, respectively. AncCA19 had the longest half-life (1.7 h) at 95 ℃ compared with existing CAs. After 2 weeks' incubation in artificial seawater at 30 ℃ or 25.0 % N-methyldiethanolamine (MDEA) at 60 ℃, the activities remained above 47,370 WAU/mg and 6,596 WAU/mg, respectively. Thus, AncCA19, as a novel benchmark of CAs, exhibits exceptional stability in a variety CCUS applications, establishing a versatile candidate for effective CO₂ capture.

Pseudomonas putida degraded 35 % of compounds in alkali-pretreated lignin liquor under nitrogen-replete conditions but with low polyhydroxyalkanoates (PHA) production, while limiting nitrogen supplement improved PHA content (PHA/dry cell weight) to 43 % at the expense of decreased lignin degradation of 22 %. Increase of initial cell biomass (0.1-1.5 g/L) monotonically improved the lignin degradation from 22 % to 33 % under nitrogen-limited conditions. Hierarchical utilization of heterogenous compounds under cell growth restricted conditions has been unveiled - simple carbon sources were prioritized for valorization, followed by aromatic compounds bioconversion. Based on the results of hierarchy and leveraging the initial bacterial biomass, acetate was augmented to facilitate one-pot lignin bioconversion under nitrogen-limited conditions. This approach improved lignin bioconversion closer to its upper degradation limit of 35 %, concomitant with PHA yield of 39 mg/g-lignin. Anaerobic digestion of lignocellulose was redesigned to favor acetate-type fermentation, with acetate constituting 91 wt%, providing an economic source of acetate.

This study integrates partial denitrification/Anammox (PD/A) with hydroxyapatite (HAP) crystallization in a single reactor, achieving simultaneous nitrogen and phosphorus removal along with phosphorus recovery. By adjusting pH, sludge concentration, low COD/TN ratio, and applying moderate dissolved oxygen stress, the system operated stably and promoted the synergistic growth of HAP and biomass. Results showed a nitrogen removal efficiency (NRE) of 94.13 % and a phosphorus removal efficiency (PRE) of 73.6 %. Metagenomic analysis revealed that under dissolved oxygen stress, The abundance of Candidatus Brocadia increased from 1 % to 26.1 %, significantly boosting anammox activity. indicating enhanced microbial activity. The upregulation of related genes (sdh, suc, hzs) further boosted AnAOB activity. HAP was identified as the main inorganic component of the granule. This process shows strong potential for nitrogen and phosphorus removal with resource recovery in wastewater treatment.

Phenazine-1,6-dicarboxylic acid (PDC) is a precursor of complex substituted phenazines used as pesticides and pharmaceuticals. The PDC biosynthesis exists the low production and the high proportion of by-products phenazine-1-carboxylic acid (PCA) derivatives in Pseudomonas P3△A. Herein, PDC production were improved by systematic metabolic engineering and synthetic regulation. The directed PDC biosynthesis was achieved by introducing the isozymes of PhzF', and PCA derivatives was barely detectable. Subsequently, a high-level PDC-producing strain P3FK2E-aF'EC was obtained by co-overexpression of aroE, phzE, phzC, and aphzF' in a multi-knock strain. Through scale-up culture, the highest PDC production and proportion reached 6,447.05 mg/L and 99.68 %, with the productivity of 89.54 mg/L·h using KB. Economically, PDC production achieved 5,584.35 mg/L accounting for 99.43 % with the highest productivity of 108.32 mg/L·h from crude glycerol. This study first achieved the directed high-level production of PDC from renewable energy, and presented a potential biosynthesis platform for PDC derivatives in Pseudomonas.

Myceliophthora thermophila stands out as a prominent fungal cell factory, garnering growing interest due to its distinctive traits advantageous. Currently, M. thermophila has been developed as an efficient cell factory, producing a variety of products from various raw materials. In this review, we firstly discuss the potential advantages of M. thermophila as a platform for metabolic engineering and industrial applications, with special emphasis on its physiological characteristics, the development of genetic modification techniques and tools, gene expression and regulation strategies. Then, the latest progress in industrial application of M. thermophila as microbial cell factory was systematically summarized, including biochemical synthesis platform, enzyme expression platform, antibody protein and vaccine production platform, bio-organic fertilizer production platform, and efficient enzyme element library. Finally, the current challenges of M. thermophila as a cell factory and its corresponding strategies are proposed, aiming to achieve green biomanufacturing of multiple products with higher efficiency.