Explore the vast range of titles available.

Polyethylene terephthalate (PET) becomes one of the most well-known polyesters and is widely used as packaging material. Recently, polyethylene terephthalate hydrolase (PETase) has emerged as a potential biocatalyst demonstrating the ability to degrade polyethylene terephthalate (PET). We showed that the rate of PETase hydrolysis could be significantly increased in the presence of hydrophobin RolA. Hydrophobins represent a class of small fungal protein that has a high surface-active substance and can spontaneously self-assemble at hydrophilic-hydrophobic interfaces. In this work, a class I hydrophobin named RolA was extracted from the mycelium pellet collected from a fermentation culture of Aspergillus oryzae. The SDS-PAGE analysis of the isolated RolA showed the presence of 11 kDa polypeptide. Recombinant PETase from Ideonella sakaiensis was also successfully expressed in Escherichia coli as a soluble protein with molecular weight approximately 30 kDa. The hydrophobin RolA could enhance the PET hydrolysis in the presence of the recombinant PETase. The hydrolysis of PET bottle by RolA-PETase achieved the highest weight loss of 26% in 4 days. It is speculated that the wetting effect of RolA acts on PET surface converts PET to become hydrophilic that leads PETase easier to contact and attack the surface.

Outer membrane vesicles (OMVs) are miniature versions of gram-negative bacteria that contain almost the same content as their parent cells, particularly in terms of membrane composition. Using OMVs as biocatalysts is a promising approach due to their potential benefits, including their ability to be handled similarly to bacteria while lacking potentially pathogenic organisms. To employ OMVs as biocatalysts, they must be functionalized with immobilized enzymes to the OMV platform. Various enzyme immobilization techniques are available, including surface display and encapsulation, each with advantages and disadvantages depending on the objectives. This review provides a concise yet comprehensive overview of these immobilization techniques and their applications in utilizing OMVs as biocatalysts. Specifically, we discuss the use of OMVs in catalyzing the conversion of chemical compounds, their role in polymer degradation, and their performance in bioremediation.

The utilization of ceramides, which are members of the sphingolipid family, has been widely acknowledged in the cosmetic and pharmaceutical industries, along with various other applications as therapeutic agents. Most ceramides currently available on the market are synthetic ceramides created through chemical reactions with precursors resembling the natural precursor of sphingolipid production by living organisms. In fact, many organisms ranging from microbes to higher-order mammals natively use metabolism to produce sphingolipids, including ceramides and their derivatives, to support cell molecular functions. Sphingolipids, for instance, are present in the cell membranes of mammals, plants, and yeast to maintain membrane morphology. As a green alternative to the chemical synthesis method, many studies have been carried out to reveal the diversity and characteristics of biologically produced ceramide derivatives. In this review, we summarized the most important aspects of ceramide biosynthesis in general and provide a quick overview of the common organisms producing ceramides. In addition, a brief discussion regarding the role of ceramides in cells and their risks was included. As the biosynthesis of ceramides is an attractive alternative to current commercial methods, the advances reviewed herein demonstrate the untapped potential for the further development of synthetic pathways to enhance biobased-ceramide production.

Summary Transforming petrochemical processes into bioprocesses has become an important goal of sustainable development. The chemical synthesis of 2,5‐furandicarboxylic acid (FDCA) from 5‐hydroxymethylfurfural (HMF) is expensive and environmentally unfavourable. The study aims to investigate a whole‐cell biocatalyst for efficient biotransformation of HMF to FDCA. For the first time, a genetically engineered Pseudomonas putida S12 strain expressing 5‐hydroxymethylfurfural oxidase (HMFO) was developed for the biocatalytic conversion of HMF to FDCA. This whole‐cell biocatalyst produced 35.7 mM FDCA from 50 mM HMF in 24 h without notable inhibition. However, when the initial HMF concentration was elevated to 100 mM, remarkable inhibition on FDCA production was observed, resulting in a reduction of FDCA yield to 42%. We solve this substrate inhibition difficulty by increasing the inoculum density. Subsequently, we used a fed‐batch strategy by maintaining low HMF concentration in the culture to maximize the final FDCA titre. Using this approach, 545 mM of FDCA was accumulatively produced after 72 hs, which is the highest production rate per unit mass of cells to the best of our knowledge. For the first time, a genetically engineered Pseudomonas putida S12 strain expressing 5‐hydroxymethylfurfural oxidase (HMFO) was developed for the biocatalytic conversion of HMF to FDCA. This whole‐cell biocatalyst produced 35.7 mM FDCA from 50 mM HMF in 24 h without notable inhibition. Using Fed‐batch approach, 545 mM of FDCA was accumulatively produced after 72 h, which is the highest production rate per unit mass of cells to the best of our knowledge.

Background The recalcitrant nature of cellulosic materials and the high cost of enzymes required for efficient hydrolysis are the major impeding steps to their practical usage for ethanol production. Ideally, a recombinant microorganism, possessing the capability to utilize cellulose for simultaneous growth and ethanol production, is of great interest. We have reported recently the use of a yeast consortium for the functional presentation of a mini-cellulosome structure onto the yeast surface by exploiting the specific interaction of different cohesin-dockerin pairs. In this study, we engineered a yeast consortium capable of displaying a functional mini-cellulosome for the simultaneous growth and ethanol production on phosphoric acid swollen cellulose (PASC). Results A yeast consortium composed of four different populations was engineered to display a functional mini-cellulosome containing an endoglucanase, an exoglucanase and a β-glucosidase. The resulting consortium was demonstrated to utilize PASC for growth and ethanol production. The final ethanol production of 1.25 g/L corresponded to 87% of the theoretical value and was 3-fold higher than a similar yeast consortium secreting only the three cellulases. Quantitative PCR was used to enumerate the dynamics of each individual yeast population for the two consortia. Results indicated that the slight difference in cell growth cannot explain the 3-fold increase in PASC hydrolysis and ethanol production. Instead, the substantial increase in ethanol production is consistent with the reported synergistic effect on cellulose hydrolysis using the displayed mini-cellulosome. Conclusions This report represents a significant step towards the goal of cellulosic ethanol production. This engineered yeast consortium displaying a functional mini-cellulosome demonstrated not only the ability to grow on the released sugars from PASC but also a 3-fold higher ethanol production than a similar yeast consortium secreting only the three cellulases. The use of more complex cellulosomal structures may further improve the overall efficiency for ethanol production.

Yarrowia lipolytica is a well-known oleaginous yeast that naturally accumulates lipids to more than 20% of their dry cell weight. Due to its brief doubling time and Generally Recognized as Safe (GRAS) properties, Y. lipolytica has been exploited for the production of commercially valuable lipids. Among the genes related to the lipid synthesis, the gene YALI0E16797g (LRO1) encoding a major triacylglycerol synthase of Y. lipolytica shows a significant impact during the acylation process. Thus, in the present work, we explore the contributions of hp4d or TEFintron promoters to the response of LRO1 expression on lipid accumulation by molecular cloning technology. Results showed that over-expression of LRO1 led to higher lipid content as well as lipid yield. The one with the hp4d promoter showed the highest lipid content of 12% wt. However, such an enhancement also caused a growth defect of cells. On the other hand, the lipid content of the cells over-expressing LRO1 with TEFintron promoter revealed only a modest increase in lipid content, but it promoted cell growth. Therefore, all things considered the one with the TEFintron promoter showed the highest lipid yield.

1,3-Propanediol (1,3-PDO) has numerous industrial applications in the synthesis of the monomer of the widely used fiber polytrimethylene terephthalate. In this work, the production of 1,3-PDO by Klebsiella pneumoniae is increased by dual-substrate cultivation and fed-batch fermentation. Experimental results indicate that the production of 1,3-PDO can be elevated to 16.09 g/L using a dual substrate ratio (of glucose to crude glycerol) of 1/30 and to 20.73 g/L using an optimized dual-substrate ratio of 1/20. Ultimately, the optimal dual-substrate feeding for a 5 L scale fed-batch fermenter that maximizes 1,3-PDO production (29.69 g/L) is determined. This production yield is better than that reported in most related studies. Eventually, the molecular weight and chemical structure of 1,3-PDO were obtained by FAB-MS, 1H-NMR, and 13C-NMR. Also, in demonstrating the effectiveness of the fermentation strategy in increasing the production and production yield of 1,3-PDO, experimental results indicate that the fermentation of 1,3-PDO is highly promising for commercialization.

Climate change is directly linked to the rapid depletion of our non-renewable fossil resources and has posed concerns on sustainability. Thus, imploring the need for us to shift from our fossil based economy to a sustainable bioeconomy centered on biomass utilization. The efficient bioconversion of lignocellulosic biomass (an ideal feedstock) to a platform chemical, such as bioethanol, can be achieved via the consolidated bioprocessing technology, termed yeast surface engineering, to produce yeasts that are capable of this feat. This approach has various strategies that involve the display of enzymes on the surface of yeast to degrade the lignocellulosic biomass, then metabolically convert the degraded sugars directly into ethanol, thus elevating the status of yeast from an immobilization material to a whole-cell biocatalyst. The performance of the engineered strains developed from these strategies are presented, visualized, and compared in this article to highlight the role of this technology in moving forward to our quest against climate change. Furthermore, the qualitative assessment synthesized in this work can serve as a reference material on addressing the areas of improvement of the field and on assessing the capability and potential of the different yeast surface display strategies on the efficient degradation, utilization, and ethanol production from lignocellulosic biomass.

Cupriavidus taiwanensis 187 is reportedly efficient in achieving the degradation of phenol and accumulation of polyhydroxybutyrate (PHB). This study attempted to optimize the cultivation conditions and fermentation strategies for phenol degradation and PHA accumulation by C. taiwanensis 187. After the cultivation conditions were optimized, the conditions required for achieving phenol degradation (100%) and PHB accumulation (51 mg/L) by C. taiwanensis 187 were identified as 30 °C and 200 rpm, when the cultivation time was around 7 h. The accumulation of PHB was further increased from 72 to 213 mg/L by feeding phenol in three rounds into the fermenter along with the exhaustion of dissolved oxygen, which could totally degrade the phenol at around 1500 mg/L. Production of PHB by C. taiwanensis 187 was confirmed by GC, 1 H-NMR, and 13 C-NMR analyses. Each analytical result proved that C. taiwanensis 187 was able to use phenol as the sole carbon source for producing PHB. Finally, these results revealed that the phenol degraded by C. taiwanensis 187 mainly contributed to cell growth rather than PHB accumulation. These results indicated that the strain C. taiwanensis 187 could be used to degrade phenol to obtain usable biological polyesters.

A mixed culture was utilized to evaluate methyl tert-butyl ether (MTBE) removal under various conditions and to isolate a MTBE-degrading pure culture. The results showed that high MTBE removal efficiencies can be reached even in the presence of other substrates. The biodegradation sequence of the target compounds by the mixed culture, in order of removal rate, was toluene, ethyl benzene, p-xylene, benzene, MTBE, ethyl ether, tert-amyl methyl ether, and ethyl tert-butyl ether. In addition, preincubation of the mixed cultures with benzene and toluene showed no negative effect on MTBE removal; on the contrary, it could even increase the degradation rate of MTBE. The kinetic behavior showed that the maximum specific growth rate and the saturation constant of the mixed culture degrading MTBE are 0.000778 h-¹ and 0.029 mg l-¹, respectively. However, a high MTBE concentration (60 mg l-¹) was slightly inhibiting to the growth of the mixed culture. The pure culture isolated from the enrichments in the bubble-air bioreactor showed better efficiency in MTBE removal than the mixed culture; whereas, tert-butyl alcohol was formed as a metabolic intermediate during the breakdown of MTBE.