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Mycobacterial phytosterol conversion naturally occurs within a vegetable oil environment, a process that has been widely adopted in water‒oil two-phase fermentation to produce active pharmaceutical intermediates of steroids. The use of hydroxypropyl-β-CD (HP-β-CD) as a potential replacement for vegetable oils has been explored. However, both approaches encounter challenges, particularly the need for a high concentration of either vegetable oil or HP-β-CD in the fermentation medium, which significantly affects the efficiency of mycobacterial phytosterol conversion as well as the recovery of the resulting products. In this study, we demonstrated that the knockout of glycerol metabolic pathways enables the utilization of glycerol as cosovlent for efficient phytosterol conversion in Mycolicibacterium neoaurum HGMS6, an industrial strain known for its production of 4-androstene-3,17-dione (4-AD). Our bioinformatic analysis revealed two parallel glycerol metabolic pathways in the HGMS6 strain. These pathways are independently initiated by glycerol kinase (GLPK) and glycerol dehydrogenase (ADHC). To investigate their roles, we conducted gene knockout experiments in which both the glycerol kinase gene ( glpk ) and the glycerol dehydrogenase gene ( adhc ) were targeted in HGMS6, resulting in the creation of a glycerol metabolism-deficient mutant, denoted HGMS6 Δadhc/Δglpk . This double mutant exhibited complete inactivation of mycobacterial glycerol metabolism without any adverse effects on mycobacterial growth when cultured in conventional fermentation medium containing glucose. We then evaluated HGMS6 Δadhc/Δglpk in an aqueous phase fermentation medium and determined that fermentation media consisting of 10% glycerol and 0.5% HP-β-CD provided the optimal conversion efficiency. In pilot-scale fermentation experiments, this mutant was highly efficient at converting phytosterols, achieving a remarkable conversion rate of up to 83.8% (mol/mol%). This bioconversion level was on par with that of HGMS6 and HGMS6 Δadhc/Δglpk when operating in vegetable oil- or HP-β-CD-containing fermentation media. This study provides a promising strategy for enhancing the efficiency of mycobacterial phytosterol conversion. Key points • The GLPK and ADHC of M. neoaurum were confirmed and examined. • The enzymology of ADHC and GLPK was characterized in vitro. • An adhc/glpk-knockout mutant efficiently converts phytosterols in fermentation media containing 10% (w/v) glycerol and 0.5% (w/v) HP-β-CD.

[This corrects the article DOI: 10.1371/journal.pone.0322838.].

In this work, limestone, aluminum nitrate hydrate, and glycerol water solution by combustion synthesis method were proposed to prepare a synthetic CaO/Ca.sub.3Al.sub.2O.sub.6 sorbent for CO.sub.2 capture in calcium looping cycles. The effects of the mass ratio of CaO to Al.sub.2O.sub.3, cycle number, carbonation conditions, and calcination conditions on the CO.sub.2 uptake by the obtained synthetic sorbent in the repeated carbonation/calcination cycles were studied in a dual fixed-bed reactor and a thermogravimetric analyzer. The optimum mass ratio of CaO to Al.sub.2O.sub.3 was 90:10 in the preparation process of the synthetic sorbent, which exhibited a 0.43 g g.sup.-1 of CO.sub.2 uptake after 50 cycles. The main compositions of the synthetic sorbent contained the mass ratio of CaO:Al.sub.2O.sub.3 = 90:10 were CaO and Ca.sub.3Al.sub.2O.sub.6, and the mass ratio of CaO to Ca.sub.3Al.sub.2O.sub.6 was 74:26. The CO.sub.2 uptake by CaO/Ca.sub.3Al.sub.2O.sub.6 increases rapidly with the carbonation time in previous 5 min and then rises slowly after 5 min. The carbonation time to reach the maximum CO.sub.2 uptake rate of CaO/Ca.sub.3Al.sub.2O.sub.6 was much sooner than that of CaO derived from limestone in each cycle. The optimum carbonation temperature window of CaO/Ca.sub.3Al.sub.2O.sub.6 was 650-700 °C. CaO/Ca.sub.3Al.sub.2O.sub.6 sorbent possessed obviously higher sintering resistance than CaO under the more severe calcination conditions in the cycles. The high CO.sub.2 uptake capacity of CaO/Ca.sub.3Al.sub.2O.sub.6 was attributed to its stable porous structure in the multiple carbonation/calcination cycles.

Crude glycerol is the main byproduct of biodiesel manufacturing from oleaginous crops and other biomass-derived oils. Approximately 10% crude glycerol is produced with every batch of biodiesel. Worldwide, there is a glut of glycerol and the price of it has decreased considerably. There are real opportunities for valorizing crude glycerol into higher value-added chemicals which can improve the economic viability of biodiesel production as an alternative fuel. Exploring new potential applications of glycerol in various sectors is needed such as in pharmaceuticals, food and beverages, cosmetics, and as a transportation fuel. However, crude glycerol produced directly from biodiesel often contains impurities that hinder its direct industrial usage and thus, a refining process is needed which is typically expensive. Hence, this review reports on current upgrading crude glycerol technologies—thermo-, bio-, physico-, and electrochemical approaches—that valorize it into higher value-added chemicals. Through comparison between those viable upgrading techniques, future research directions, challenges, and advantages/disadvantage of the technologies are described. Electrochemical technology, which is still underdeveloped in this field, is highlighted, due to its simplicity, low maintenance cost, and it working in ambient condition, as it shows promising potential to be applied as a major glycerol upgrading technique.

GNAT family homologs are widespread and diverse in their use of acyl-CoAs to acylate small molecules and proteins, functions difficult to predict based on in silico analysis alone. Here, we reveal a critical role for lysine acetylation in archaeal central carbon metabolism, identifying the GNAT family Pat2 of Haloferax volcanii as essential for long-term survival on glycerol (compared to glucose) and capable of mediating the lysine acetylation of glycerol kinase, a key enzyme in glycerol metabolism. Pat2 residues important for catalytic activity and a putative regulatory partner (HVO_2384) are also identified. The findings expand our understanding of GNAT family acyltransferases and highlight conserved mechanisms of metabolic control by post-translational modification across domains of life.

This technical report describes a method to clear fixed brain tissues while allowing for fluorescent dye tracing and retaining cellular morphology. The authors demonstrate the utility of the technique by obtaining a wiring diagram for sister mitral cells. We report a water-based optical clearing agent, SeeDB, which clears fixed brain samples in a few days without quenching many types of fluorescent dyes, including fluorescent proteins and lipophilic neuronal tracers. Our method maintained a constant sample volume during the clearing procedure, an important factor for keeping cellular morphology intact, and facilitated the quantitative reconstruction of neuronal circuits. Combined with two-photon microscopy and an optimized objective lens, we were able to image the mouse brain from the dorsal to the ventral side. We used SeeDB to describe the near-complete wiring diagram of sister mitral cells associated with a common glomerulus in the mouse olfactory bulb. We found the diversity of dendrite wiring patterns among sister mitral cells, and our results provide an anatomical basis for non-redundant odor coding by these neurons. Our simple and efficient method is useful for imaging intact morphological architecture at large scales in both the adult and developing brains.

► Glycerol is an abundant and inexpensive carbon source generated as a by-product of biofuel production. ► High degree of reduction of glycerol enables increased yields of fuels and reduced chemicals. ► Current efforts exploit glycerol for the microbial production of numerous compounds. ► Future research efforts will expand the portfolio of available products. To ensure the long-term viability of biorefineries, it is essential to go beyond the carbohydrate-based platform and develop complementing technologies capable of producing fuels and chemicals from a wide array of available materials. Glycerol, a readily available and inexpensive compound, is generated during biodiesel, oleochemical, and bioethanol production processes, making its conversion into value-added products of great interest. The high degree of reduction of carbon atoms in glycerol confers the ability to produce fuels and reduced chemicals at higher yields when compared to the use of carbohydrates. This review focuses on current engineering efforts as well as the challenges involved in the utilization of glycerol as a carbon source for the production of fuels and chemicals.

A series of novel functional polycarbonates, specifically poly(solketal glycidyl ether carbonate-co-propylene carbonate)s with varying compositions, were synthesized through the ring-opening copolymerization of solketal glycidyl ether, propylene oxide, and carbon dioxide. The reaction was catalyzed by rac-(salcy)Co[sup.III]X complexes with bis(triphenylphosphine)iminium salts as co-catalysts, achieving high selectivity. The resulting terpolymers exhibited number-average molecular weights ranging from 2 × 10[sup.4] to 1 × 10[sup.5] and a narrow, bimodal molecular weight distribution, with dispersities of 1.02–1.07 for each mode. Interestingly, the addition of a small amount of water to the reaction mixture yielded a terpolymer with a unimodal molecular weight distribution and a dispersity of 1.11. Subsequent acidic hydrolysis of the solketal protective groups produced poly(glyceryl glycerol carbonate-co-propylene carbonate). All terpolymers were amorphous, with Tg near or below room temperature. The hydroxyl-functional polycarbonates underwent cyclodepolymerization under milder conditions compared to polycarbonates with protected hydroxyl groups.