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Poly(3-hydroxybutyrate) (PHB) is a biobased and biodegradable plastic. Considering the environmental issues of petroleum-based plastics, PHB is promising as it can be degraded in a relatively short time by bacteria to water and carbon dioxide. Substantial efforts have been made to identify PHB-degrading bacteria. To identify PHB-degrading bacteria, solid-based growth or clear zone assays using PHB as the sole carbon source are the easiest methods; however, PHB is difficult to dissolve and distribute evenly, and bacteria grow slowly on PHB plates. Here, we suggest an improved PHB plate assay using cell-grown PHB produced by Halomonas sp. and recovered by sodium dodecyl sulfate (SDS). Preparation using SDS resulted in evenly distributed PHB plates that could be used for sensitive depolymerase activity screening in less time compared with solvent-melted pellet or cell-grown PHB. With this method, we identified 15 new strains. One strain, Cutibacterium sp. SOL05 (98.4% 16S rRNA similarity to Cutibacterium acne), showed high PHB depolymerase activity in solid and liquid conditions. PHB degradation was confirmed by clear zone size, liquid culture, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The results indicate this method can be used to easily identify PHB-degrading bacteria from various sources to strengthen the benefits of bioplastics.

Cadaverine, 1,5-diaminopentane, is one of the most promising chemicals for biobased-polyamide production and it has been successfully produced up to molar concentration. Pyridoxal 5′-phosphate (PLP) is a critical cofactor for inducible lysine decarboxylase (CadA) and is required up to micromolar concentration level. Previously the regeneration of PLP in cadaverine bioconversion has been studied and salvage pathway pyridoxal kinase (PdxY) was successfully introduced; however, this system also required a continuous supply of adenosine 5′-triphosphate (ATP) for PLP regeneration from pyridoxal (PL) which add in cost. Herein, to improve the process further a method of ATP regeneration was established by applying baker’s yeast with jhAY strain harboring CadA and PdxY, and demonstrated that providing a moderate amount of adenosine 5′-triphosphate (ATP) with the simple addition of baker’s yeast could increase cadaverine production dramatically. After optimization of reaction conditions, such as PL, adenosine 5′-diphosphate, MgCl2, and phosphate buffer, we able to achieve high production (1740 mM, 87% yield) from 2 M l-lysine. Moreover, this approach could give averaged 80.4% of cadaverine yield after three times reactions with baker’s yeast and jhAY strain. It is expected that baker’s yeast could be applied to other reactions requiring an ATP regeneration system.

Poly(3-hydroxybutyrate) (PHB) is a common polyhydroxyalkanoate (PHA) with potential as an alternative for petroleum-based plastics. Previously, we reported a new strain, Halomonas sp. YLGW01, which hyperproduces PHB with 94% yield using fructose. In this study, we examined the PHB production machinery of Halomonas sp. YLGW01 in more detail by deep-genome sequencing, which revealed a 3,453,067-bp genome with 65.1% guanine-cytosine content and 3054 genes. We found two acetyl-CoA acetyltransferases (Acetoacetyl-CoA thiolase, PhaA), one acetoacetyl-CoA reductase (PhaB), two PHB synthases (PhaC1, PhaC2), PHB depolymerase (PhaZ), and Enoyl-CoA hydratase (PhaJ) in the genome, along with two fructose kinases and fructose transporter systems, including the phosphotransferase system (PTS) and ATP-binding transport genes. We then examined the PHB production by Halomonas sp. YLGW01 using high-fructose corn syrup (HFCS) containing fructose, glucose, and sucrose in sea water medium, resulting in 7.95 ± 0.11 g/L PHB (content, 67.39 ± 0.34%). PHB was recovered from Halomonas sp. YLGW01 using different detergents; the use of Tween 20 and SDS yielded micro-sized granules with high purity. Overall, these results reveal the distribution of PHB synthetic genes and the sugar utilization system in Halomonas sp. YLGW01 and suggest a possible method for PHB recovery.

Psychrophilic bacteria, living at low and mild temperatures, can contribute significantly to our understanding of microbial responses to temperature, markedly occurring in the bacterial membrane. Here, a newly isolated strain, Pseudomonas sp. B14-6, was found to dynamically change its unsaturated fatty acid and cyclic fatty acid content depending on temperature which was revealed by phospholipid fatty acid (PLFA) analysis. Genome sequencing yielded the sequences of the genes Δ-9-fatty acid desaturase (desA) and cyclopropane-fatty acid-acyl-phospholipid synthase (cfa). Overexpression of desA in Escherichia coli led to an increase in the levels of unsaturated fatty acids, resulting in decreased membrane hydrophobicity and increased fluidity. Cfa proteins from different species were all found to promote bacterial growth, despite their sequence diversity. In conclusion, PLFA analysis and genome sequencing unraveled the temperature-related behavior of Pseudomonas sp. B14-6 and the functions of two membrane-related enzymes. Our results shed new light on temperature-dependent microbial behaviors and might allow to predict the consequences of global warming on microbial communities.

γ-Aminobutyric acid (GABA), an important fine chemical in pharmacotherapy and food industries, is used as a novel material in the nylon industry and has attracted attention for its potential application in large scale production. Search for new genes and strains, development of efficient reaction systems, such as fermentation and bioconversion, and use of cheap starting material like monosodium glutamate (MSG) can make GABA production using less expensive bulk chemicals possible. Therefore, in this study, we constructed a recombinant Escherichia coli whole-cell system for GABA production that expressed glutamate decarboxylase (GAD) from Lactobacillus brevis and used MSG as the starting material. We also optimized the reaction conditions for MSG to GABA conversion, such as citrate buffer concentration, pyridoxal 5′te concentration, temperature, MSG concentration, and cell density (OD600). The optimized whole-cell system converted MSG to GABA via seven repetitive cycles resulting in an average conversion rate of 86% (71.7 mM/h) within 42 h.

One of the advantages of microbial synthesis of polyhydroxyalkanoates (PHAs) is the production of diverse polymers with different properties by the addition of different monomers, such as 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), and 3-hydroxyhexanoate (3HHx). Considering the number of possible variables, terpolymers can have more variations than copolymers. In this study, we aimed to synthesize the terpolymer P(3HB-co-3HV-co-3HHx) from volatile fatty acids such as propionate and butyrate using the recombinant Ralstonia eutropha strain (Re2133/pCB81), containing deletions in the phaB1, phaB2, and phaB3 genes, and overexpression of synthetic PHA operon (phaC2, phaA, phaJ). This strain produced terpolymers depending on the ratio of two different carbon sources, namely, propionic and butyric acids; however, wild type R. eutropha could not produce the same type of polymer. The incorporation of 3-hydroxyvalerate and 3-hydroxyhexanoate monomers was confirmed by gas chromatography and H-nuclear magnetic resonance spectroscopy, and the parameters affecting the terpolymer composition were obtained based on regression. In addition, the thermal analysis showed that this terpolymer has properties different from those of the copolymer, obtained from the same composition of volatile acids. Depending on the ratio of two volatile acids, the composition of the terpolymer can be regulated resulting in different properties.

Streptomyces spp. have been isolated from different environmental niches and are known to exhibit diversity in secondary metabolism. They have complex regulation system to control secondary metabolism, however it is difficult to prioritize the importance of specific regulator among the thousands of global or cluster-situated genes that may regulate secondary metabolism in different Streptomyces strains. Here we suggest a simple homology-based selection method to find out important regulators by comparing seven Streptomyces strains finding highly homologous regulators in various Streptomyces strains and showed highly homologous 11 regulators containing four well known regulators such as BldM, IclR, WhiD and NdgR. Among various regulators, we showed a putative transcriptional regulator in Streptomyces coelicolor A3(2), SCO1463 playing a pivotal role in growth, antibiotic production (actinorhodin[ACT] and undecylprodigiosin [RED] production), and production/utilization of organic acids such as propionate and succinate by making comparisons between the deletion mutant and the wild type strain. Although high homology in various strains does not always mean the importance of a gene, we suggested a criterion on which regulator should be studied first and which would be more important among more than one thousand regulators.

Polyhydroxybutyrate (PHB), the most well-known polyhydroxyalkanoate, is a bio-based, biodegradable polymer that has the potential to replace petroleum-based plastics. Lignocellulose hydrolysate, a non-edible resource, is a promising substrate for the sustainable, fermentative production of PHB. However, its application is limited by the generation of inhibitors during the pretreatment processes. In this study, we investigated the feasibility of PHB production in E. coli in the presence of inhibitors found in lignocellulose hydrolysates. Our results show that the introduction of PHB synthetic genes (bktB, phaB, and phaC from Ralstonia eutropha H16) improved cell growth in the presence of the inhibitors such as furfural, 4-hydroxybenzaldehyde, and vanillin, suggesting that PHB synthetic genes confer resistance to these inhibitors. In addition, increased PHB production was observed in the presence of furfural as opposed to the absence of furfural, suggesting that this compound could be used to stimulate PHB production. Our findings indicate that PHB production using lignocellulose hydrolysates in recombinant E. coli could be an innovative strategy for cost-effective PHB production, and PHB could be a good target product from lignocellulose hydrolysates, especially glucose.

A novel marine bacterium Arenibacter palladensis YHY2 isolated from Eastern Sea, South Korea revealed hydrolysing ability of crab chitin in shake flask and microbial fuel cell (MFC) systems. Under shake flask cultivation, strain YHY2 demonstrated 71.44 ± 1.90 U/ml chitinase activity with the microbial cell optical density (OD) 0.699 ± 0.021. High performance liquid chromatography (HPLC) results showed N-acetylglucosamine (GlcNAc) as the major by-product of chitin degradation. Furthermore, Ralstonia eutropha H16 which has carbon utilization limited to GlcNAc and fructose was co-cultivated with YHY2 to consume GlcNAc and accumulate polyhydroxyalkanoates (PHA). However, on co-cultivating strain YHY2 with H16 surprisingly showed higher production of chitinase (97.89 ± 2.72 U/ml) and GlcNAc (80.31 mg GlcNAc/g chitin) corresponding to the microbial cell OD (1.065 ± 0.005) at 120 h. In addition, marine strain YHY2 demonstrated biofilm formation, hence co-cultivation of strain YHY2 and H16 under MFC system was performed to check the electricity production. Maximum electricity current output density was 15.15 μA/cm2 at the initial stage and 10.72 μA/cm2 at 204 h. GlcNAc (196.34 mg GlcNAc/g chitin) was produced along with other metabolites like butyrate, acetate, lactate, and propionate in MFC system. The microbial cell biomass from MFC was analysed for PHA content showed 1.020 g/l of 3-polyhydroxybutyrate (PHB) and 0.198 g/l of 3-polyhydroxyvalerate (PHV) as the main components of PHA. Moreover, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were performed to reveal changes in chitin before and after degradation. Thus, the exploitation of recalcitrant chitin biomass for simultaneous production of GlcNAc, electricity, and PHA in one-pot MFC system was the productive asset for sustainable development.

Polyhydroxybutyrates (PHB) are biodegradable polymers that are produced by various microbes, including Ralstonia, Pseudomonas, and Bacillus species. In this study, a Vibrio proteolyticus strain, which produces a high level of polyhydroxyalkanoate (PHA), was isolated from the Korean marine environment. To determine optimal growth and production conditions, environments with different salinity, carbon sources, and nitrogen sources were evaluated. We found that the use of a medium containing 2% (w/v) fructose, 0.3% (w/v) yeast extract, and 5% (w/v) sodium chloride (NaCl) in M9 minimal medium resulted in high PHA content (54.7%) and biomass (4.94 g/L) over 48 h. Addition of propionate resulted in the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(HB-co-HV)) copolymer as propionate acts as a precursor for the HV unit. In these conditions, the bacteria produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) containing a 15.8% 3HV fraction with 0.3% propionate added as the substrate. To examine the possibility of using unsterilized media with high NaCl content for PHB production, V. proteolyticus was cultured in sterilized and unsterilized conditions. Our results indicated a higher growth, leading to a dominant population in unsterilized conditions and higher PHB production. This study showed the conditions for halophilic PHA producers to be later implemented at a larger scale.

Arctic bacteria employ various mechanisms to survive harsh conditions, one of which is to accumulate carbon and energy inside the cell in the form of polyhydroxyalkanoate (PHA). Whole-genome sequencing of a new Arctic soil bacterium Pseudomonas sp. B14-6 revealed two PHA-production-related gene clusters containing four PHA synthase genes (phaC). Pseudomonas sp. B14-6 produced poly(6% 3-hydroxybutyrate-co-94% 3-hydroxyalkanoate) from various carbon sources, containing short-chain-length PHA (scl-PHA) and medium-chain-length PHA (mcl-PHA) composed of various monomers analyzed by GC-MS, such as 3-hydroxybutyrate, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate, 3-hydroxydodecenoic acid, 3-hydroxydodecanoic acid, and 3-hydroxytetradecanoic acid. By optimizing the PHA production media, we achieved 34.6% PHA content using 5% fructose, and 23.7% PHA content using 5% fructose syrup. Differential scanning calorimetry of the scl-co-mcl PHA determined a glass transition temperature (Tg) of 15.3 °C, melting temperature of 112.8 °C, crystallization temperature of 86.8 °C, and 3.82% crystallinity. In addition, gel permeation chromatography revealed a number average molecular weight of 3.6 × 104, weight average molecular weight of 9.1 × 104, and polydispersity index value of 2.5. Overall, the novel Pseudomonas sp. B14-6 produced a polymer with high medium-chain-length content, low Tg, and low crystallinity, indicating its potential use in medical applications.

Polyhydroxyalkanoates (PHAs) are attractive new bioplastics for the replacement of plastics derived from fossil fuels. With their biodegradable properties, they have also recently been applied to the medical field. As poly(3-hydroxybutyrate) produced by wild-type Ralstonia eutropha has limitations with regard to its physical properties, it is advantageous to synthesize co- or terpolymers with medium-chain-length monomers. In this study, tung oil, which has antioxidant activity due to its 80% α-eleostearic acid content, was used as a carbon source and terpolymer P(53 mol% 3-hydroxybytyrate-co-2 mol% 3-hydroxyvalerate-co-45 mol% 3-hydroxyhexanoate) with a high proportion of 3-hydroxyhexanoate was produced in R. eutropha Re2133/pCB81. To avail the benefits of α-eleostearic acid in the tung oil-based medium, we performed partial harvesting of PHA by using a mild water wash to recover PHA and residual tung oil on the PHA film. This resulted in a film coated with residual tung oil, showing antioxidant activity. Here, we report the first application of tung oil as a substrate for PHA production, introducing a high proportion of hydroxyhexanoate monomer into the terpolymer. Additionally, the residual tung oil was used as an antioxidant coating, resulting in the production of bioactive PHA, expanding the applicability to the medical field.

In the present study, an exopolysaccharide (EPS)-producing bacterial strain was isolated from the Eastern Sea (Sokcho Beach) of South Korea and identified as Sphingobium yanoikuyae BBL01. Media optimization was performed using response surface design, and a yield of 2.63 ± 0.02 g/L EPS was achieved. Purified EPS produced using lactose as the main carbon source was analyzed by GC–MS and found to be composed of α-D-xylopyranose (28.6 ± 2.0%), β-D-glucopyranose (21.0 ± 1.6%), α-D-mannopyranose (18.5 ± 1.2%), β- d -mannopyranose (13.1 ± 1.4%), β-D-xylopyranose (10.2 ± 2.1%), α- d -talopyranose (5.9 ± 1.1%), and β- d -galacturonic acid (2.43 ± 0.8%). Interestingly, different carbon sources (glucose, galactose, glycerol, lactose, sucrose, and xylose) showed no effect on EPS monomer composition, with a slight change in the mass percentage of various monosaccharides. Purified EPS was stable up to 233 °C, indicating its possible suitability as a thickening and gelling agent for food-related applications. EPS also showed considerable emulsifying, flocculating, free-radical scavenging, and metal-complexion activity, suggesting various biotechnological applications.

Pipecolic acid, a non-proteinogenic amino acid, is a metabolite in lysine metabolism and a key chiral precursor in local anesthesia and macrolide antibiotics. To replace the environmentally unfriendly chemical production or preparation procedure of pipecolic acid, many biological synthetic routes have been studied for a long time. Among them, synthesis by lysine cyclodeaminase (LCD), encoded by pipA, has several advantages, including stability of enzyme activity and NAD+ self-regeneration. Thus, we selected this enzyme for pipecolic acid biosynthesis in a whole-cell bioconversion. To construct a robust pipecolic acid production system, we investigated important conditions including expression vector, strain, culture conditions, and other reaction parameters. The most important factor was the introduction of multiple pipA genes into the whole-cell system. As a result, we produced 724 mM pipecolic acid (72.4 % conversion), and the productivity was 0.78 g/L/h from 1 M l-lysine after 5 days. This is the highest production reported to date.

Methicillin-resistant Staphylococcus aureus (MRSA) strains are distinct from general Staphylococcus strains with respect to the composition of the membrane, ability to form a thicker biofilm, and, importantly, ability to modify the target of antibiotics to evade their activity. The agr gene is an accessory global regulator of gram-positive bacteria that governs virulence or resistant mechanisms and is therefore an important target for the control of resistant strains. However, the mechanism by which agr impacts factors affecting resistance to β-lactam antibiotics remains unclear. In the present study, we found an Δagr mutant strain with higher resistance to high concentrations of b-lactam antibiotics such as oxacillin and ampicillin. To determine the influence of variation in the microenvironment of cells between the parental and mutant strains, fatty acid analysis of the supernatant, total lipids, and phospholipid fatty acids were compared. The Δagr mutant strain tended to produce fewer fatty acids and retained lower amounts of C16, C18 fatty acids in the supernatant. Phospholipid analysis showed a dramatic increase in the hydrophobic longer-chain fatty acids in the membranes. To target these differences in fatty acid distribution and membrane composition, we applied several surfactants and found that sorbitan trioleate (Span85) had a synergistic effect with oxacillin by decreasing biofilm formation and growth. These findings indicate that agr suppression allows for MRSA to antagonize antibiotics via several changes, including constant expression of mecA, fatty acid metabolism and distribution, and biofilm thickening, resulting in a strain with higher resistance to β-lactam antibiotics.

Bacteria from the genus Halomonas hold promise in biotechnology as sources of salt-tolerant enzymes, biosurfactants, biopolymers, osmolytes, and as actors in bioremediation processes. In a previous work, we have identified Halomonas socia strain CKY01 having various hydrolase activities. Here, we aimed to study the survival strategies of marine bacteria. A deep genome sequencing study of H. socia CKY01 has revealed 4627 genes reaching 4,753,299 bp with 64 % of GC content. This strain produced polyhydroxybutyrate (PHB) having one gene clusters having phaC and phasin, and it has several genes responsible for the uptake, synthesis, and transport of the osmolytes such as betaine, choline, ectoine, carnitine, and proline in the bacterial genome. The addition of 60 mM glutamate, 60 mM proline and 60 mM ectoine enhanced growth 300.8 %, 294.2 % and 235.0 %, respectively, under 10 % saline conditions. In particular, ectoine and proline increased salt resistance and allowed cells to survive in more than 15 % NaCl. By combining experimental and genome sequencing data, we have investigated the importance of osmolytes on the survival of this Halomonas strain.

Glutaric acid is one of the promising C5 platform compounds in the biochemical industry. It can be produced chemically, through the ring-opening of butyrolactone followed by hydrolysis. Alternatively, glutaric acid can be produced via lysine degradation pathways by microorganisms. In microorganisms, the overexpression of enzymes involved in this pathway from E. coli and C. glutamicum has resulted in high accumulation of 5-aminovaleric acid. However, the conversion from 5-aminovaleric acid to glutaric acid has resulted in a relatively low conversion yield for unknown reasons. In this study, as a solution to improve the production of glutaric acid, we introduced gabTD genes from B. subtilis to E. coli for a whole cell biocatalytic approach. This approach enabled us to determine the effect of co-factors on reaction and to achieve a high conversion yield from 5-aminovaleric acid at the optimized reaction condition. Optimization of whole cell reaction by different plasmids, pH, temperature, substrate concentration, and cofactor concentration achieved full conversion with 100 mM of 5-aminovaleric acid to glutaric acid. Nicotinamide adenine dinucleotide phosphate (NAD(P)+) and α-ketoglutaric acid were found to be critical factors in the enhancement of conversion in selected conditions. Whole cell reaction with a higher concentration of substrates gave 141 mM of glutaric acid from 300 mM 5-aminovaleric acid, 150 mM α-ketoglutaric acid, and 60 mM NAD+ at 30 °C, with a pH of 8.5 within 24 h (47.1% and 94.2% of conversion based on 5-aminovaleric acid and α-ketoglutaric acid, respectively). The whole cell biocatalyst was recycled 5 times with the addition of substrates; this enabled the accumulation of extra glutaric acid.

Polyhydroxyalkanoates (PHA), such as poly (3-hydroxybutyrate) (PHB), have emerged as potential alternatives to petroleum-based plastics and can be produced through the appropriate selection of marine bacteria that are already adapted to high salt and low temperature conditions without the requirement of antibiotic treatment. The present study, thus, aimed to screen and characterize thirteen PHA-producing microbial strains isolated from the Gwangalli beach in Busan, South Korea. Among them, Halomonas sp. YLGW01 produced the highest amount of PHB (94.6 ± 1.8% (w/w)) using fructose. Interestingly Halomonas sp. YLGW01 showed increase in cell size (8.39 ± 3.63 μm) with fructose as carbon source as compared to glucose (2.34 ± 0.44 μm). Fructose syrup was investigated as carbon source under unsterilized conditions and 95.26 ± 1.78% of PHB was produced. Overall, this strain showed the highest PHB contents in halotolerant bacteria.

Itaconic acid is an important organic acid and a major component of various polymers. It is used in resins, superabsorbent polymers, and substitutes for petrochemicalbased monomers such as acrylic and methacrylic acids. Itaconic acid is primarily produced by the fungus Aspergillus terreus, which yields a high titer with albeit long fermentation period and by-products. In our previous study, Escherichia coli JY001 was reported to produce itaconic acid using citric acid in whole-cell reaction resulting in higher itaconic acid productivity with less by-products formation. The present study aimed to increase whole-cell enzyme stability and reusability, via immobilization of E. coli JY001 using barium-alginate beads. We optimized the cations, temperature, pH, alginate, BaCl2 concentration, cell density per bead, and CTAB content to improve transfer rate of substrates and products. Under the optimized conditions, immobilized whole cells were stable for four repeated cycles of itaconic acid production. The present results would strengthen the basis for a continuous itaconic acid production.

Bacteria have evolved a defense system to resist external stressors, such as heat, pH, and salt, so as to facilitate survival in changing or harsh environments. However, the specific mechanisms by which bacteria respond to such environmental changes are not completely elucidated. Here, we used halotolerant bacteria as a model to understand the mechanism conferring high tolerance to NaCl. We screened for genes related to halotolerance in Halomonas socia, which can provide guidance for practical application. Phospholipid fatty acid analysis showed that H. socia cultured under high osmotic pressure produced a high portion of cyclopropane fatty acid derivatives, encoded by the cyclopropane-fatty acid-acyl phospholipid synthase gene (cfa). Therefore, H. socia cfa was cloned and introduced into Escherichia coli for expression. The cfa-overexpressing E. coli strain showed better growth, compared with the control strain under normal cultivation condition as well as under osmotic pressure (> 3% salinity). Moreover, the cfa-overexpressing E. coli strain showed 1.58-, 1.78-, 3.3-, and 2.19-fold higher growth than the control strain in the presence of the inhibitors furfural, 4-hydroxybenzaldehyde, vanillin, and acetate from lignocellulosic biomass pretreatment, respectively. From a practical application perspective, cfa was co-expressed in E. coli with the polyhydroxyalkanoate (PHA) synthetic operon of Ralstonia eutropha using synthetic and biosugar media, resulting in a 1.5-fold higher in PHA production than that of the control strain. Overall, this study demonstrates the potential of the cfa gene to boost cell growth and production even in heterologous strains under stress conditions.

Rhodococcus sp. YHY01 was studied to utilize various lignin derived aromatic compounds. It was able to utilize p-coumaric acid, cresol, and 2,6 dimethoxyphenol and resulted in biomass production i.e. 0.38 g dcw/L, 0.25 g dcw/L and 0.1 g dcw/L, and lipid accumulation i.e. 49%, 40%, 30%, respectively. The half maximal inhibitory concentration (IC50) value for p-coumaric acid (13.4 mM), cresol (7.9 mM), and 2,6 dimethoxyphenol (3.4 mM) was analyzed. Dimethyl sulfoxide (DMSO) solubilized barley straw lignin fraction was used as a carbon source for Rhodococcus sp. YHY01 and resulted in 0.130 g dcw/L with 39% w/w lipid accumulation. Major fatty acids were palmitic acid (C16:0) 51.87%, palmitoleic acid (C16:l) 14.90%, and oleic acid (C18:1) 13.76%, respectively. Properties of biodiesel produced from barley straw lignin were as iodine value (IV) 27.25, cetane number (CN) 65.57, cold filter plugging point (CFPP) 14.36, viscosity (υ) 3.81, and density (ρ) 0.86.

Odd chain fatty acids serve as anti-allergic, anti-inflammatory, and antifungal agents, and are useful for the production of biodiesel. Rhodococcus sp. YHY01 utilizes a wide range of carbon sources and accumulate lipids i.e. fructose (37% w/w dcw) glucose (56% w/w dcw), glycerol (50% w/w dcw), acetate (42% w/w dcw), butyrate (65% w/w dcw), lactate (56% w/w dcw), and propionate (62% w/w dcw). In this study, propionate was proved as the best carbon source and produced 69% odd chain fatty acids of total fatty acids, followed by glycerol (13% odd chain fatty acids of total fatty acids). A synthetic medium optimized with response surface design containing glycerol, propionate, and ammonium chloride (0.32%:0.76%:0.040% w/v) facilitated the production of total fatty acids 69% w/w of dcw, and odd chain fatty acids comprised 85% w/w of total fatty acids. Major odd chain fatty acids were in the order C17:0 > C15:0 > Cis-10-C17:1 > 10Me-C17:0 > C19:0 > Cis-10-C19:1.

Ralstonia eutropha Re2133/pCB81 is able to utilize various volatile fatty acids (VFAs) (acetate, butyrate, lactate, and propionate) for polyhydroxyalkanoates (PHAs) production. Acetate and lactate resulted in poly(3-hydroxybutyrate) P(3HB) production, butyrate in poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) P(3HB-co-3HHx), and propionate in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(3-HB-co-3HV). Various biomass yields i.e. (Yx/s, 0.131 ± 0.02 g/g acetate, 0.221 ± 0.02 g/g butyrate, 0.222 ± 0.05 g/g lactate, and 0.225 ± 0.04 g/g propionate) and PHA yields (Yp/s, 0.01 ± 0.001 g/g acetate, 0.11 ± 0.004 g/g butyrate, 0.03 ± 0.001 g/g lactate, and 0.18 ± 0.005 g/g propionate) were observed with the different organic acids. When all the organic acids were mixed together R. eutropha Re2133/pCB81 had the following order of preference; lactate > butyrate > propionate > acetate. A response surface design study showed that in mixtures butyrate is the main organic acid involved in PHA production and acts as a precursor for HHx monomer units to produce copolymer P(3HB-co-3HHx). Food waste ferment (FWF) without any additional nitrogen source and precursors resulted in P(3HB-co-3HHx) accumulation (52 ± 4% w/w with 18.5 ± 3% HHx fraction).

Many poultry eggs are discarded worldwide because of infection (i.e., avian flu) or presence of high levels of pesticides. The possibility of adopting egg yolk as a source material to produce polyhydroxyalkanoate (PHA) biopolymer was examined in this study. Cupriavidus necator Re2133/pCB81 was used for the production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or poly(3HHx), a polymer that would normally require long-chain fatty acids as carbon feedstocks for the incorporation of 3HHx monomers. The optimal medium contained 5% egg yolk oil and ammonium nitrate as a nitrogen source, with a carbon/nitrogen (C/N) ratio of 20. Time course monitoring using the optimized medium was conducted for 5 days. Biomass production was 13.1 g/l, with 43.7% co-polymer content. Comparison with other studies using plant oils and the current study using egg yolk oil revealed similar polymer yields. Thus, discarded egg yolks could be a potential source of PHA.

The overuse of antibiotics has led to the emergence of multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA). MRSA is difficult to kill with a single antibiotic because it has evolved to be resistant to various antibiotics by increasing the PBP2a (mecA) expression level, building up biofilm, introducing SCCmec for multidrug resistance, and changing its membrane properties. Therefore, to overcome antibiotic resistance and decrease possible genetic mutations that can lead to the acquisition of higher antibiotic resistance, drug combination therapy was applied based on previous results indicating that MRSA shows increased susceptibility to free fatty acids and surfactants. The optimal ratio of three components and the synergistic effects of possible combinations were investigated. The combinations were directly applied to clinically isolated strains, and the combination containing 15 &mu, g/mL of oxacillin was able to control SCCmec type III and IV isolates having an oxacillin minimum inhibitory concentration (MIC) up to 1024 &mu, g/mL, moreover, the combination with a slightly increased oxacillin concentration was able to kill SCCmec type II. Phospholipid analysis revealed that clinical strains with higher resistance contained a high portion of 12-methyltetradecanoic acid (anteiso-C15:0) and 14-methylhexadecanoic acid (anteiso-C17:0), although individual strains showed different patterns. In summary, we showed that combinatorial therapy with a low concentration of oxacillin controlled different laboratory and highly diversified clinical MRSA strains.

Glutaric acid is a promising alternative chemical to phthalate plasticizer since it can be produced by the bioconversion of lysine. Though, recent studies have enabled the high-yield production of its precursor, 5-aminovaleric acid (AMV), glutaric acid production via the AMV pathway has been limited by the need for cofactors. Introduction of NAD(P)H oxidase (Nox) with GabTD enzyme remarkably diminished the demand for oxidized nicotinamide adenine dinucleotide (NAD+ ). Supply of oxygen through vigorous shaking had a significant effect on the conversion of AMV with a reduced requirement of NAD + . A high conversion rate was achieved in Nox coupled GabTD reaction under optimized expression vector, terrific broth (TB), and pH 8.5 at high cell density. Supplementary expression of GabD resulted in the production of 353 ± 35 mM glutaric acid with 88.3 ± 8.7% conversion from 400 mM AMV. Moreover, the reaction with a higher concentration of AMV could produce 528 ± 21 mM glutaric acid with 66.0 ± 2.7% conversion. In addition, the co-biotransformation strategy of GabTD and DavBA whole cells could produce 282 mM glutaric acid with 70.8% conversion from lysine, compared to the 111 mM glutaric acid yield from the combined GabTD-DavBA system.