In this review, we presented the industrial status of biomanufactured polyhydroxyalkanoates (PHA), including poly (3-hydroxybutyrate) (PHB), poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly (3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB)), and poly (3-hydroxybutyrate-3-hydroxycaproate) (PHBH). A lot of modification studies, aimed at solving problems of poor thermal stability, narrow processing window and other drawbacks of PHA, are discussed. The properties of PHA can be optimized by using proper modification method, in order to expand its applications.
3-Hydroxybutyric Acid ; Biotechnology ; Hydroxybutyrates ; Polyesters ; Polyhydroxyalkanoates ; chemistry

The present study aimed to unravel the carbon metabolism pathway of Acinetobacter sp. TAC-1, a heterotrophic nitrification-aerobic denitrification (HN-AD) strain that utilizes poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as a carbon source. Sodium acetate was employed as a control to assess the gene expression of carbon metabolic pathways in the TAC-1 strain. The results of genome sequencing demonstrated that the TAC-1 strain possessed various genes encoding carbon metabolic enzymes, such as gltA, icd, sucAB, acs, and pckA. KEGG pathway database analysis further verified the presence of carbon metabolism pathways, including the glycolytic pathway (EMP), pentose phosphate pathway (PPP), glyoxylate cycle (GAC), and tricarboxylic acid (TCA) cycle in the TAC-1 strain. The differential expression of metabolites derived from distinct carbon sources provided further evidence that the carbon metabolism pathway of TAC-1 utilizing PHBV follows the sequential process of PHBV (via the PPP pathway)→gluconate (via the EMP pathway)→acetyl-CoA (entering the TCA cycle)→CO₂+H₂O (generating electron donors and releasing energy). This study is expected to furnish a theoretical foundation for the advancement and implementation of novel denitrification processes based on HN-AD and solid carbon sources.
3-Hydroxybutyric Acid ; Carbon/metabolism* ; Polyesters ; Hydroxybutyrates ; Metabolic Networks and Pathways

Poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] belongs to the polyhydroxyalkanoates (PHA) family and possesses promising properties including biocompatibility and biodegradability. In this study, we directly synthesized P(3HB-co-LA) with glucose by introducing the β-ketothiolase and acetoacetyl-CoA reductase from Ralstonia eutropha, the engineered propionate CoA transferase from Clostridium propionicum and the engineered polyhydroxyalkanoate synthase from Pseudomonas fluorescens strain 2P24 into Escherichia coli. The polymer content was 83.9% (W/W), and the molar percentage of lactate reached 1.6%. On this basis, in order to accumulate lactate, we reduced the activity of respiratory chain by deleting the ubiX gene, which is involved in the synthesis of coenzyme Q8. Moreover, we removed the dld gene to avoid the conversion of lactate to pyruvate during the fermentation. With these manipulations, the molar percentage of lactate in the polymer was improved to 14.1%, with an 81.7% (W/W) of polymer content. The test results indicated that the strategy of reducing the activity of respiratory chain effectively increased the lactate units in the polymer, and it contributed a new approach to change the content of monomer components in the polymer.
3-Hydroxybutyric Acid ; Electron Transport ; Escherichia coli ; Lactic Acid ; Metabolic Engineering ; Polyesters

In this study, the Autokit Total Ketone Bodies kit (Wako Pure Chemical, Japan), a total ketone measurement assay using an enzymatic method, was evaluated using a Roche Cobas e702 instrument (Roche Diagnostics, Germany). Precision, linearity, carryover, and reference range verification were evaluated with reference to Clinical Laboratory Standards Institute guidelines. Standard materials provided by the manufacturer and patient samples were used for the evaluation. The precision and carryover of the evaluation result satisfied the acceptance criteria. Linearity was also acceptable at more than 0.99. The quantitative Autokit Total Ketone Bodies kit is precise, and can be widely used in clinical laboratories.
3-Hydroxybutyric Acid ; Evaluation Studies as Topic ; Humans ; Ketone Bodies* ; Methods ; Reference Values

Escherichia coli was metabolically engineered to produce poly(glycolate-co-lactate-co-3-hydroxybutyrate) using glucose and xylose as carbon sources. The combinatorial biosynthetic route was constructed by the overexpression of a series of enzymes including D-tagatose 3-epimerase, L-fuculokinase, L-fuculose-phosphate aldolase, aldehyde dehydrogenase, propionyl-CoA transferase, β-ketothiolase, acetoacetyl-CoA reductase, and polyhydroxyalkanoate synthase. Overexpression of polyhydroxyalkanoate granule associated protein significantly improved biopolymer synthesis, and the recombinant strain reached 3.73 g/L cell dry weight with 38.72% (W/W) biopolymer content. A co-culture engineering strategy was developed to produce biopolymer from a mixture of glucose and xylose, achieving 4.01 g/L cell dry weight containing 21.54% (W/W) biopolymer. The results of this work offer an approach for simultaneously utilizing glucose and xylose and indicate the potential for future biopolymer production from lignocellulosic biomass.
3-Hydroxybutyric Acid ; Escherichia coli ; Glucose ; Glycolates ; Lactates ; Metabolic Engineering ; Polyesters ; Xylose

PURPOSE: Despite decades of clinical experience with the ketogenic diet (KD), its efficacy and mechanisms of action have been examined in few animal studies. The present study was designed to investigate the effect of a KD on flurothyl-induced seizure susceptibility in rats. METHODS: Twenty male Sprague-Dawley rats were divided into two equal groups. Dietary treatment was initiated at P39. The experimental group was fasted for a day and then fed a KD consisting of [fat] : [protein + carbohydrate] ratio of 4.3 : 1, while the control group was fed a standard rodent chow. On treatment day 21, blood beta-hydroxybutyrate (BHB) levels were assayed and seizures were chemically induced by flurothyl (40 micro l/min). Seizure susceptibility was defined as the latency from the start of flurothyl infusion to the onset of a generalized seizure (loss of posture with bilateral hindlimb tonic extension). Shorter latencies reflect greater seizure susceptibility. RESULTS: Blood BHB levels in the KD-treated group were significantly higher than those of the control group (4.75+/-0.38 [n=10] vs. 0.19+/-0.02 [n=10] mM, respectively ; p<0.01). The latencies to the onset of a generalized seizure were 673.2+/-32.95 [n=10] and 523.0+/-31.11 [n=10] seconds for the KD-treated and control groups, respectively (p<0.01). CONCLUSION: This study demonstrates the significant decrease in the susceptibility of flurothyl-induced seizure in the KD-treated rats. Furthermore, we have established a working animal model from which future mechanistic studies can be based.
3-Hydroxybutyric Acid ; Animals ; Flurothyl ; Hindlimb ; Humans ; Ketogenic Diet* ; Male ; Models, Animal ; Posture ; Rats ; Rats, Sprague-Dawley ; Rodentia ; Seizures*

Polyhydroxyalkanoates (PHAs), as a novel class of biopolymer, are attracting more attention due to their diverse material properties and environment-independent biodegradability. Here we report the preparation of PHA exhibiting efficient antibacterial activity by embedding Nisin, a food additive generally recognized as safe, into poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), a type of PHA with high biocompatibility. We first prepared Nisin-containing PHBHHx films using solvent casting method. Confocal laser scanning microscopy analysis showed that a well-mixed integrated structure of the films with an even distribution of the Nisin particles in the PHBHHx matrices. Then the antimicrobial activity of PHBHHx/Nisin films against Micrococcus luteus was quantified on agar plate by measuring the size of inhibition zone. Cultivation in liquid media further confirmed the releasing of Nisin from the films and the long-time antibacterial activity. Results showed that the threshold of Nisin concentration for long-time and effective inhibition against bacteria growth is 25 μg/g. These results altogether establish a technological foundation for the application of PHA in biomedicine and food industry.
3-Hydroxybutyric Acid ; chemistry ; Anti-Bacterial Agents ; chemistry ; Caproates ; chemistry ; Micrococcus luteus ; drug effects ; Nisin ; chemistry ; Polyhydroxyalkanoates ; chemistry

PURPOSE: The ketogenic diet (KD) remains a therapy in search of explanation although it is an established treatment for patients with intractable seizures. It was designed to mimic the biochemical changes seen upon fasting, specifically the formation of ketone bodies: acetoacetate (ACA), beta-hydroxybutyrate (BHB), and to a lesser extent, acetone. The present study was designed to investigate the protective effect of BHB on flurothyl-induced seizures in rats. METHODS: Thirty-four male Sprague-Dawley rats were divided into two equal groups. Experimental rats (n=17) were injected intraperitoneally with BHB (20 mmol/kg), while control animals (n=17) with normal saline. Fifteen minutes later, seizures were chemically induced by flurothyl infusion (40 mL/min). Seizure susceptibility was defined as the latency from the start of flurothyl infusion to the onset of a generalized seizure. Shorter latencies reflected greater seizure susceptibility. RESULTS: The mean (+/- SEM) latency to the onset of a generalized seizure in the experimental animals treated with BHB was 476.5 +/- 13.9 seconds, which was significantly longer (P < 0.05) than the control (438.0 +/- 10.5 seconds). CONCLUSION: This study demonstrated the significant decrease in flurothyl-induced seizure susceptibility in rats treated with BHB. Our results suggest that BHB may be directly anticonvulsant.
3-Hydroxybutyric Acid ; Acetoacetates ; Acetone ; Animals ; Fasting ; Flurothyl ; Humans ; Hydrazines ; Ketogenic Diet ; Male ; Rats ; Rats, Sprague-Dawley ; Seizures

OBJECTIVETo explore the method of fabricating larynx-shape tissue engineered cartilage by means of filling together with wrapping with pedicle myofascial flap.

METHODSSerial steps of solution casting, extrusion molding and particulate leaching were used to make larynx-shape [poly (3-hydroxybutyrate-co-3-hydroxyhexanoate), PHBHH] biomaterial models. The chondrocytes were seeded onto PHBHH models to form cell-PHBHH composites for culture in vitro for one week and then to fill and wrap larynx-shape composites with pedicle myofascial flap. After that to implant larynx-shape composites in situ on the back of adult New Zealand white rabbits (experimental groups n = 9). Control groups (n = 3) were the same measure as experimental groups but without chondrocytes on PHBHH models. Finally, morphological observation, HE & special staining and immunohistochemical test were conducted to evaluate the cartilage regeneration and its shape at 6, 8 and 12 weeks following implantation.

RESULTSThe PHBHH models appeared to be hollow half-trumpet with edges and corners of larynx-shape and its porosity > 90%. Pedicle myofascial flap using fascia as lining presented rich blood supply and had enough to fill and wrap larynx-shape composites. Tissue engineered larynx-shape cartilage specimens could be harvested at different period. It was demonstrated that the cartilaginous tissue formed in 6 weeks after implantation through histological and immunohistochemical examination and further maturity in 12 weeks and 18 weeks. But no cartilaginous tissue showed without chondrocytes on PHBHH as control groups to implant at the same time.

CONCLUSIONIt seems that pedicled myofascial flap showed sufficient blood supply and that the filling together with wrapping method with pedicled myofascial flap is appropriate for fabricating larynx-shape tissue engineered cartilage.

3-Hydroxybutyric Acid ; Animals ; Cartilage ; Cell Culture Techniques ; Fascia ; transplantation ; Larynx, Artificial ; Rabbits ; Surgical Flaps ; Tissue Engineering ; methods ; Tissue Scaffolds

OBJECTIVETo establish of blood beta hydroxybutyrate (βOHB) threshold for diagnosing type 2 diabetes ketoacidosis (DKA) and explore the relationship between βOHB levels and the severity of DKA.

METHODSCorrelation analysis was performed between serum βOHB and [HCO(3)] in type 2 diabetic patients admitted in the emergency department in the past year. Regression equation was used to calculate the concentration of βOHB corresponding to a [HCO(3)] level of 18.0, 15, and 10.0 mmol/L, and βOHB concentration corresponding to a [HCO(3)] level of 18.0 mmol/l was used as the DKA diagnostic threshold.

RESULTSThe serum βOHB level and [HCO3] concentration showed a good correlation (R²=0.7023, P<0.001). βOHB concentrations that corresponded to a [HCO(3)] level of 18.0, 15, and 10.0 mmol/L were 3.0, 4.70, and 7.5 mmol/L, respectively, in accordance with the severity of DKA. Combined with the blood glucose concentration ≥ 13.9 mmol/L, a blood βOHB≥3.0 mmol/L showed a sensitivity of 99%, specificity of 86%, and total effectiveness of 92.81% for diagnosing DKA.

CONCLUSIONA serum βOHB level above 3.0 mmol/L can be used as the diagnostic threshold of DKA. βOHB can serve as an index for assessing the severity of DKA.

3-Hydroxybutyric Acid ; blood ; Diabetes Mellitus, Type 2 ; blood ; Diabetic Ketoacidosis ; blood ; diagnosis ; Humans ; Sensitivity and Specificity ; Severity of Illness Index