Lipase from Yarrowia lipolytica: Production, characterization and application as an industrial biocatalyst

UV mutagenesis for lipase overproduction from Bacillus cereus ATA179, nutritional optimization, characterization and its usability in the detergent industry

In this study, the wild-type Bacillus cereus ATA179 was mutagenized by random UV mutagenesis to increase lipase production. The mutant with maximum lipolytic activity was named Bacillus cereus EV4. The mutant strain (10.6 U/mL at 24 h) produced 60% more enzyme than the wild strain (6.6 U/mL at 48 h). Nutritional factors on lipase production were investigated. Sucrose was the best carbon source, (NH4)2HPO4 was the best nitrogen source and CuSO4 was the best metal ion source. Mutant EV4 showed a 32% increase in lipase production in the modified medium. The optimum temperature and pH were found to be 60 °C and 7.0, respectively. CuSO4, CaCl2, LiSO4, KCl, BaCl2, and Tween 20 had an activating effect on the enzyme. Vmax and Km values were found to be 17.36 U/mL and 0.036 mM, respectively. The molecular weight was determined as 28.2 kDa. The activity of lipase was found to be stable up to 60 days at 20 °C, 75 days at 4 °C, and 90 days at -20 °C. The potential of lipase in the detergent industry was investigated. The enzyme was not affected by detergent additives but was effective in removing stains in fabrics contaminated with oily substances.

Marine-Derived Lipases for Enhancing Enrichment of Very-Long-Chain Polyunsaturated Fatty Acids with Reference to Omega-3 Fatty Acids

Omega-3 fatty acids are essential fatty acids that are not synthesised by the human body and have been linked with the prevention of chronic illnesses such as cardiovascular and neurodegenerative diseases. However, the current dietary habits of the majority of the population include lower omega-3 content compared to omega-6, which does not promote good health. To overcome this, pharmaceutical and nutraceutical companies aim to produce omega-3-fortified foods. For this purpose, various approaches have been employed to obtain omega-3 concentrates from sources such as fish and algal oil with higher amounts of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Among these techniques, enzymatic enrichment using lipase enzymes has gained tremendous interest as it is low in capital cost and simple in operation. Microorganism-derived lipases are preferred as they are easily produced due to their higher growth rate, and they hold the ability to be manipulated using genetic modification. This review aims to highlight the recent studies that have been carried out using marine lipases for the enrichment of omega-3, to provide insight into future directions. Overall, the covalent bond-based lipase immobilization to various support materials appears most promising; however, greener and less expensive options need to be strengthened.

Transcriptomics aids in uncovering the metabolic shifts and molecular machinery of Schizochytrium limacinum during biotransformation of hydrophobic substrates to docosahexaenoic acid

BACKGROUND

Biotransformation of waste oil into value-added nutraceuticals provides a sustainable strategy. Thraustochytrids are heterotrophic marine protists and promising producers of omega (ω) fatty acids. Although the metabolic routes for the assimilation of hydrophilic carbon substrates such as glucose are known for these microbes, the mechanisms employed for the conversion of hydrophobic substrates are not well established. Here, thraustochytrid Schizochytrium limacinum SR21 was investigated for its ability to convert oils (commercial oils with varying fatty acid composition and waste cooking oil) into ω-3 fatty acid; docosahexaenoic acid (DHA).

RESULTS

Within 72 h SR21 consumed ~ 90% of the oils resulting in enhanced biomass (7.5 g L- 1) which was 2-fold higher as compared to glucose. Statistical analysis highlights C16 fatty acids as important precursors of DHA biosynthesis. Transcriptomic data indicated the upregulation of multiple lipases, predicted to possess signal peptides for secretory, membrane-anchored and cytoplasmic localization. Additionally, transcripts encoding for mitochondrial and peroxisomal β-oxidation along with acyl-carnitine transporters were abundant for oil substrates that allowed complete degradation of fatty acids to acetyl CoA. Further, low levels of oxidative biomarkers (H2O2, malondialdehyde) and antioxidants were determined for hydrophobic substrates, suggesting that SR21 efficiently mitigates the metabolic load and diverts the acetyl CoA towards energy generation and DHA accumulation.

CONCLUSIONS

The findings of this study contribute to uncovering the route of assimilation of oil substrates by SR21. The thraustochytrid employs an intricate crosstalk among the extracellular and intracellular molecular machinery favoring energy generation. The conversion of hydrophobic substrates to DHA can be further improved using synthetic biology tools, thereby providing a unique platform for the sustainable recycling of waste oil substrates.

Applications of Bacillus subtilis Protein Display for Medicine, Catalysis, Environmental Remediation, and Protein Engineering

Bacillus subtilis spores offer several advantages that make them attractive for protein display. For example, protein folding issues associated with unfolded polypeptide chains crossing membranes are circumvented. In addition, they can withstand physical and chemical extremes such as heat, desiccation, radiation, ultraviolet light, and oxidizing agents. As a result, the sequence of the displayed protein can be easily obtained even under harsh screening conditions. Next, immobilized proteins have many economic and technological advantages. They can be easily separated from the reaction and the protein stability is increased in harsh environments. In traditional immobilization methods, proteins are expressed and purified and then they are attached to a matrix. In contrast, immobilization occurs naturally during the sporulation process. They can be easily separated from the reaction and the protein stability is increased in harsh environments. Spores are also amenable to high-throughput screening for protein engineering and optimization. Furthermore, they can be used in a wide array of biotechnological and industrial applications such as vaccines, bioabsorbants to remove toxic chemicals, whole-cell catalysts, bioremediation, and biosensors. Lastly, spores are easily produced in large quantities, have a good safety record, and can be used as additives in foods and drugs.

Effect of Yarrowia lipolytica yeast biomass with increased kynurenic acid content on selected metabolic indicators in mice

Background

The unconventional yeast species Yarrowia lipolytica is a valuable source of protein and many other nutrients. It can be used to produce hydrolytic enzymes and metabolites, including kynurenic acid (KYNA), an endogenous metabolite of tryptophan with a multidirectional effect on the body. The administration of Y. lipolytica with an increased content of KYNA in the diet may have a beneficial effect on metabolism, which was evaluated in a nutritional experiment on mice.

Methods

In the dry biomass of Y. lipolytica S12 enriched in KYNA (high-KYNA yeast) and low-KYNA (control) yeast, the content of KYNA was determined by high-performance liquid chromatography. Then, proximate and amino acid composition and selected indicators of antioxidant status were compared. The effect of 5% high-KYNA yeast content in the diet on the growth, hematological and biochemical indices of blood and the redox status of the liver was determined in a 7-week experiment on adult male mice from an outbred colony derived from A/St, BALB/c, BN/a and C57BL/6J inbred strains.

Results

High-KYNA yeast was characterized by a greater concentration of KYNA than low-KYNA yeast (0.80 ± 0.08 vs. 0.29 ± 0.01 g/kg dry matter), lower content of crude protein with a less favorable amino acid composition and minerals, higher level of crude fiber and fat and lower ferric-reducing antioxidant power, concentration of phenols and glutathione. Consumption of the high-KYNA yeast diet did not affect the cumulative body weight gain per cage, cumulative food intake per cage and protein efficiency ratio compared to the control diet. A trend towards lower mean corpuscular volume and hematocrit, higher mean corpuscular hemoglobin concentration and lower serum total protein and globulins was observed, increased serum total cholesterol and urea were noted. Its ingestion resulted in a trend towards greater ferric-reducing antioxidant power in the liver and did not affect the degree of liver lipid and protein oxidation.

Conclusions

The improvement of the quality of Y. lipolytica yeast biomass with increased content of KYNA, including its antioxidant potential, would be affected by the preserved level of protein and unchanged amino acid profile. It will be worth investigating the effect of such optimized yeast on model animals, including animals with metabolic diseases.

Energetic and Kinetic Origins of CALB Interfacial Activation Revealed by PaCS-MD/MSM

The conformational dynamics of Candida antarctica lipase B (CALB) was investigated by molecular dynamics (MD) simulation, parallel cascade selection MD (PaCS-MD), and the Markov state model (MSM) and mainly focused on the lid-opening motion closely related to substrate binding. All-atom MD simulation of CALB was conducted in water and on the interface of water and tricaprylin. CALB initially situated in water and separated by layers of water from the interface is spontaneously adsorbed onto the tricaprylin surface during MD simulation. The opening and closing motions of the lid are simulated by PaCS-MD, and subsequent MSM analysis provided the free-energy landscape and time scale of the conformational transitions among the closed, semiopen, and open states. The closed state is the most stable in the water system, but the stable conformation in the interface system shifts to the semiopen state. These effects could explain the energetics and kinetics origin of the previously reported interfacial activation of CALB. These findings could help expand the application of CALB toward a wide variety of substrates.

Bio-Based Materials versus Synthetic Polymers as a Support in Lipase Immobilization: Impact on Versatile Enzyme Activity

To improve enzyme stability, the immobilization process is often applied. The choice of a support on which the enzymes are adsorbed plays a major role in enhancing biocatalysts’ properties. In this study, bio-based (i.e., chitosan, coffee grounds) and synthetic (i.e., Lewatit VP OC 1600) supports were used in the immobilization of lipases of various microbial origins (yeast (Yarrowia lipolytica) and mold (Aspergillus oryzae)). The results confirmed that the enzyme proteins had been adsorbed on the surface of the selected carriers, but not all of them revealed comparably high catalytic activity. Immobilized CALB (Novozym 435) was used as a commercial reference biocatalyst. The best hydrolytic activity (higher than that of CALB) was observed for Novozym 51032 (lipase solution of A. oryzae) immobilized on Lewatit VP OC 1600. In terms of synthetic activity, there were only slight differences between the applied carriers for A. oryzae lipase, and the highest measures were obtained for coffee grounds. All of the biocatalysts had significantly lower activity in the synthesis reactions than the reference catalyst.

Selection of Yarrowia lipolytica Strains as Possible Solution to Valorize Untreated Cheese Whey

Cheese whey management and disposal is a major issue for dairy industries due to its high level of chemical and biochemical oxygen demand. However, it can still represent a source of nutrients (i.e., sugars, proteins and lipids) that can be applied, among other options, as substrate for microbial growth. Yarrowia lipolytica can grow in different environments, consuming both hydrophilic and hydrophobic substrates, and tolerates high salt concentrations. In this work, the lipolytic and proteolytic profile of 20 strains of Y. lipolytica were tested on caseins and butter. Then, their growth potential was evaluated in four types of whey (caciotta, ricotta, squacquerone and their mix). Y. lipolytica showed a very strain-dependent behavior for both hydrolytic profiles and growth capabilities on the different substrates. The best growers for all the types of whey tested were PO1, PO2, and RO2, with the first one reaching up to 8.77 log cfu/mL in caciotta whey after 72 h. The volatile molecule profile of the samples incubated with the best growers were characterized by higher amounts of esters, acids, ketones and alcohols. In this way, cheese whey can become a source of microbial cultures exploitable in the dairy sector.

Yarrowia lipolytica as an Alternative and Valuable Source of Nutritional and Bioactive Compounds for Humans

Yarrowia lipolytica, an oleagineous species of yeast, is a carrier of various important nutrients. The biomass of this yeast is an extensive source of protein, exogenous amino acids, bioavailable essenctial trace minerals, and lipid compounds as mainly unsaturated fatty acids. The biomass also contains B vitamins, including vitamin B12, and many other bioactive components. Therefore, Y. lipolytica biomass can be used in food supplements for humans as safe and nutritional additives for maintaining the homeostasis of the organism, including for vegans and vegetarians, athletes, people after recovery, and people at risk of B vitamin deficiencies.

Lipases as Effective Green Biocatalysts for Phytosterol Esters’ Production: A Review

Lipases are versatile enzymes widely used in the pharmaceutical, cosmetic, and food industries. They are green biocatalysts with a high potential for industrial use compared to traditional chemical methods. In recent years, lipases have been used to synthesize a wide variety of molecules of industrial interest, and extraordinary results have been reported. In this sense, this review describes the important role of lipases in the synthesis of phytosterol esters, which have attracted the scientific community’s attention due to their beneficial effects on health. A systematic search for articles and patents published in the last 20 years with the terms “phytosterol AND esters AND lipase” was carried out using the Scopus, Web of Science, Scielo, and Google Scholar databases, and the results showed that Candida rugosa lipases are the most relevant biocatalysts for the production of phytosterol esters, being used in more than 50% of the studies. The optimal temperature and time for the enzymatic synthesis of phytosterol esters mainly ranged from 30 to 101 °C and from 1 to 72 h. The esterification yield was greater than 90% for most analyzed studies. Therefore, this manuscript presents the new technological approaches and the gaps that need to be filled by future studies so that the enzymatic synthesis of phytosterol esters is widely developed.

Metabolic engineering Yarrowia lipolytica for a dual biocatalytic system to produce fatty acid ethyl esters from renewable feedstock in situ and in one pot

Given the grave concerns over increasing consumption of petroleum resources and dramatic environmental changes arising from carbon dioxide emissions worldwide, microbial biosynthesis of fatty acid ethyl ester (FAEE) biofuels as renewable and sustainable replacements for petroleum-based fuels has attracted much attention. As one of the most important microbial chassis, the nonconventional oleaginous yeast Yarrowia lipolytica has emerged as a paradigm organism for the production of several advanced biofuels and chemicals. Here, we report the engineering of Y. lipolytica for use as an efficient dual biocatalytic system for in situ and one-pot production of FAEEs from renewable feedstock. Compared to glucose with 5.7% (w/w) conversion rate to FAEEs, sunflower seed oil in the culture medium was efficiently used to generate FAEEs with 84% (w/w) conversion rate to FAEEs by the engineered Y. lipolytica strain GQY20 that demonstrates an optimized intercellular heterologous FAEE synthesis pathway. In particular, the titer of extracellular FAEEs from sunflower seed oil reached 9.9 g/L, 10.9-fold higher than that with glucose as a carbon source. An efficient dual biocatalytic system combining ex vivo and strengthened in vitro FAEE production routes was constructed by overexpression of a lipase (Lip2) variant in the background strain GQY20, which further increased FAEEs levels to 13.5 g/L. Notably, deleting the ethanol metabolism pathway had minimal impact on FAEE production. Finally, waste cooking oil, a low-cost oil-based substance, was used as a carbon source for FAEE production in the Y. lipolytica dual biocatalytic system, resulting in production of 12.5 g/L FAEEs. Thus, the developed system represents a promising green and sustainable process for efficient biodiesel production. KEY POINTS: • FAEEs were produced by engineered Yarrowia lipolytica. • A Lip2 variant was overexpressed in the yeast to create a dual biocatalytic system. • Waste cooking oil as a substrate resulted in a high titer of 12.5 g/L FAEEs.

Supplementation of Bile Acids and Lipase in Broiler Diets for Better Nutrient Utilization and Performance: Potential Effects and Future Implications – A Review

Bile acids are used for better emulsification, digestion and absorption of dietary fat in chicken, especially in early life. Similarly, exogenous lipases have also been used for the improvement of physiological limitation of the chicken digestive system. Owing to potential of both bile acids and lipases, their use has been increased in recent years, for better emulsification of dietary fat and improvement of growth performance in broilers. In the past, pancreatic lipases were used for supplementation, but recently, microbial lipase is getting attention in poultry industry as a hydrolysis catalyst. Bile acids strengthen the defence mechanism of body against bacterial endotoxins and also play a key role in lipid regulation and sugar metabolism as signaling molecules. It has been demonstrated that bile acids and lipases may improve feed efficiency by enhancing digestive enzyme activity and ultimately leading to better fat digestion and absorption. Wide supplemental range of bile acids (0.004% to 0.25%) and lipases (0.01% to 0.1%) has been used in broiler diets for improvement of fat digestibility and their performance. Combinations of different bile acids have shown more potential to improve feed efficiency (by 7.14%) even at low (0.008%) levels as compared to any individual bile acid. Lipases at a lower level of 0.03% have exhibited more promising potential to improve fat digestibility and feed efficiency. However, contradicting results have been published in literature, which needs further investigations to elucidate various nutritional aspects of bile acids and lipase supplementation in broiler diet. This review focuses on providing insight on the mechanism of action and potential application of bile acids and lipases in broiler diets. Moreover, future implications of these additives in poultry nutrition for enhancing nutrient utilization and absorption are also discussed.

Integrated Cleaner Biocatalytic Process for Biodiesel Production from Crude Palm Oil Comparing to Refined Palm Oil

An integrated cleaner biocatalyst process was performed for biodiesel production from crude palm oil (CPO) and refined palm oil (RPO). It was evaluated on process efficiency in terms of high purity of biodiesel as well as by-products without purification, less wastewater, less time consuming, and a simple downstream process. A first saponification step was carried out in both f CPO and RPO, a high purity of glycerol (86.25% and 87.5%) was achieved, respectively, while free fatty acids (FFASs) in soap were obtained after hexane extraction. High yields of FFASs were obtained from both CPO and RPO (98.83% and 90.94%). Subsequently, the FFAs were esterified to biodiesel by a biocatalyst of immobilized lipase. The highest biodiesel yields achieved were of 92.14% and 92.58% (CPO and RPO). Remarkably, biodiesel yields obtained from CPO and RPO achieved satisfactory values and the biocatalyst used could be reused for more than 16–17 cycles.

Studies on the Catalytic Properties of Crude Freeze-Dried Preparations of Yarrowia lipolytica Extracellular Lipases for Geranyl Ester Derivative Synthesis

The study aimed to evaluate the impact of selected factors of the freeze-drying process on the hydrolytic and synthetic activity of the extracellular lipases of Y. lipolytica KKP 379 and to attempt the use of the crude enzyme preparation as a biocatalyst in the synthesis of geranyl 4-hydroxyphenylpropanoate. Antioxidant and antibacterial properties of the geranyl ester derivative were also investigated in order to evaluate their usefulness as a novel food additive. The studies confirmed that freeze-drying was an effective method of dehydrating yeast supernatant and allowed for obtaining lyophilizates with low water activity from 0.055 to 0.160. The type and concentration of the additive (2-6% whey protein hydrolyzate, 0.5% and 1% ammonium sulphate) had a significant effect on the hydrolytic activity of enzyme preparations, while the selected variants of drying temperature during the freeze-drying process were not significant (10 °C and 50 °C). Low yield of geranyl 4-hydroxyphenylopropionate was shown when the lyophilized supernatant was used (5.3%), but the yield of ester synthesis increased when the freeze-dried Y. lipolytica yeast biomass was applied (47.9%). The study confirmed the antioxidant properties of the synthesized ester by the DPPH• and CUPRAC methods, as well as higher antibacterial activity against tested bacteria than its precursor with 0.125 mM MIC (minimal inhibitory concentration) against L. monocytogenes.

Waste soybean frying oil for the production, extraction, and characterization of cell-wall-associated lipases from Yarrowia lipolytica

The lipolytic yeast Yarrowia lipolytica produces cell-wall-associated lipases, namely Lip7p and Lip8p, that could have interesting properties as catalyst either in free (released lipase fraction-RLF) or cell-associated (cell-bound lipase fraction-CBLF) forms. Herein, a mixture of waste soybean frying oil, yeast extract and bactopeptone was found to favor the enzyme production. Best parameters for lipase activation and release from the cell wall by means of acoustic wave treatment were defined as: 26 W/cm2 for 1 min for CBLF and 52 W/cm2 for 2 min for RLF. Optimal pH and temperature values for lipase activity together with storage conditions were similar for both the free enzyme and cell-associated one: pH 7.0; T = 37 °C; and > 70% residual activity for 60 days at 4, - 4 °C and for 15 days at 30 °C.

Sustainable Lipase Production by Diutina rugosa NRRL Y-95 Through a Combined Use of Agro-Industrial Residues as Feedstock

The potential use of alternative culture media towards the development of a sustainable bioprocess to produce lipases by Diutina rugosa is clearly demonstrated. First, a synthetic medium containing glucose, peptone, yeast extract, oleic acid, and ammonium sulfate was proposed, with lipase activity of 143 U/L. Then, alternative culture media formulated with agro-industrial residues, such as molasses, corn steep liquor (CSL), and olive mill waste (OMW), were investigated. An experimental design was conducted, and only CSL concentration was found to have a positive effect in lipase production. The highest lipase activity (561 U/L) was produced on a mixture of molasses (5 g/L), CSL (6 g/L), OMW (0.5% v/v), 0.5 g/L of ammonium sulfate, and 3 g/L of peptone at 24 h of cultivation. Lipase production was also carried out in a 1-L bioreactor leading to a slightly higher lipase activity at 24 h of cultivation. The semi-purified enzyme exhibits an optimum temperature and pH of 40 °C and 7.0, respectively. Finally, the media cost per unit of lipase produced (UPC) was influenced by the medium components, specially by the inducer used. The lowest UPC was obtained when the agro-industrial residues were combined and used at the improved concentrations.

Main Structural Targets for Engineering Lipase Substrate Specificity

Microbial lipases represent one of the most important groups of biotechnological biocatalysts. However, the high-level production of lipases requires an understanding of the molecular mechanisms of gene expression, folding, and secretion processes. Stable, selective, and productive lipase is essential for modern chemical industries, as most lipases cannot work in different process conditions. However, the screening and isolation of a new lipase with desired and specific properties would be time consuming, and costly, so researchers typically modify an available lipase with a certain potential for minimizing cost. Improving enzyme properties is associated with altering the enzymatic structure by changing one or several amino acids in the protein sequence. This review detailed the main sources, classification, structural properties, and mutagenic approaches, such as rational design (site direct mutagenesis, iterative saturation mutagenesis) and direct evolution (error prone PCR, DNA shuffling), for achieving modification goals. Here, both techniques were reviewed, with different results for lipase engineering, with a particular focus on improving or changing lipase specificity. Changing the amino acid sequences of the binding pocket or lid region of the lipase led to remarkable enzyme substrate specificity and enantioselectivity improvement. Site-directed mutagenesis is one of the appropriate methods to alter the enzyme sequence, as compared to random mutagenesis, such as error-prone PCR. This contribution has summarized and evaluated several experimental studies on modifying the substrate specificity of lipases.

Biodegradation of slop oil by endophytic Bacillus cereus EN18 coupled with lipase from Rhizomucor miehei (Palatase®)

Removal of slop oil, a by-product of oil refining, also obtained in cleaning up of oil tanks and filters is a difficult issue. High content of hydrocarbons (C3-C40) and other organic compounds makes this waste difficult to eliminate from the environment. The purpose of this investigation was to combine bacterial degradation by endophytic Bacillus cereus EN18 with biotransformation performed using lipase enzyme preparation (Palatase®) to remove recalcitrant compounds present in slop oil from the environment. Endophytic B. cereus EN18 was able to biodegrade up to 40% of slop oil while supplementation with lipase improved the efficiency of contamination removal in about one third. Also the use of lipase enzyme preparation resulted in higher microbial activity of B. cereus EN18 bacterial strain, as well as higher concentration of fatty acids in the culture medium, which indicates higher degradation efficiency. Obtained results suggest that lipase preparation from Rhizomucor miehei (Palatase®) may be a useful agent to improve microbial degradation of recalcitrant pollutants, like slop oil in water environments. GC and spectrometric analysis revealed that hydrocarbons from slop oil were effectively degraded while using both microbial degradation and lipase catalysis.

Enzyme Immobilization on Nanomaterials for Biosensor and Biocatalyst in Food and Biomedical Industry

Enzymes exhibit a great catalytic activity for several physiological processes. Utilization of immobilized enzymes has a great potential in several food industries due to their excellent functional properties, simple processing and cost effectiveness during the past decades. Though they have several applications, they still exhibit some challenges. To overcome the challenges, nanoparticles with their unique physicochemical properties act as very attractive carriers for enzyme immobilization. The enzyme immobilization method is not only widely used in the food industry but is also a component methodology in the pharmaceutical industry. Compared to the free enzymes, immobilized forms are more robust and resistant to environmental changes. In this method, the mobility of enzymes is artificially restricted to changing their structure and properties. Due to their sensitive nature, the classical immobilization methods are still limited as a result of the reduction of enzyme activity. In order to improve the enzyme activity and their properties, nanomaterials are used as a carrier for enzyme immobilization. Recently, much attention has been directed towards the research on the potentiality of the immobilized enzymes in the food industry. Hence, the present review emphasizes the different types of immobilization methods that is presently used in the food industry and other applications. Various types of nanomaterials such as nanofibers, nanoflowers and magnetic nanoparticles are significantly used as a support material in the immobilization methods. However, several numbers of immobilized enzymes are used in the food industries to improve the processing methods which not only reduce the production cost but also the effluents from the industry.

Biosynthetic strategies to produce xylitol: an economical venture

Xylitol is a natural five-carbon sugar alcohol with potential for use in food and pharmaceutical industries owing to its insulin-independent metabolic regulation, tooth rehardening, anti-carcinogenic, and anti-inflammatory, as well as osteoporosis and ear infections preventing activities. Chemical and biosynthetic routes using D-xylose, glucose, or biomass hydrolysate as raw materials can produce xylitol. Among these methods, microbial production of xylitol has received significant attention due to its wide substrate availability, easy to operate, and eco-friendly nature, in contrast with high-energy consuming and environmental-polluting chemical method. Though great advances have been made in recent years for the biosynthesis of xylitol from xylose, glucose, and biomass hydrolysate, and the yield and productivity of xylitol are substantially improved by metabolic engineering and optimizing key metabolic pathway parameters, it is still far away from industrial-scale biosynthesis of xylitol. In contrary, the chemical synthesis of xylitol from xylose remains the dominant route. Economic and highly efficient xylitol biosynthetic strategies from an abundantly available raw material (i.e., glucose) by engineered microorganisms are on the hard way to forwarding. However, synthetic biology appears as a novel and promising approach to develop a super yeast strain for industrial production of xylitol from glucose. After a brief overview of chemical-based xylitol production, we critically analyzed and comprehensively summarized the major metabolic strategies used for the enhanced biosynthesis of xylitol in this review. Towards the end, the study is wrapped up with current challenges, concluding remarks, and future prospects for designing an industrial yeast strain for xylitol biosynthesis from glucose.

Improvement of lipase activity by synergistic immobilization on polyurethane and its application for large-scale synthesizing vitamin A palmitate

We have developed an improved and effective method to immobilize lipase on hydrophobic polyurethane foam (PUF) with different modifications. PUF was treated with hydrochloric acid to increase the active sites and then the active carboxyl groups and amino groups were exposed. Enzyme activity of lipase immobilized on PUF-HCL (8000 U/g) was 50% higher than that of lipase immobilized on PUF (5300 U/g). There is an increase in the activity of the immobilized lipase on AA/PEI-modified support (115,000 U/g), a 2.17-fold increase compared to lipase immobilized on the native support was observed. The activity of immobilized lipases was dependent on the PEI molecular weight, with best results from enzyme immobilized on PUF-HCL-AA/PEI (MW 70,000 Da, 12,800 U/g)), which was 2.41 times higher compared to that of the same enzyme immobilized on PUF. These results suggest that the activity of immobilized lipase is influenced by the support surface properties, and a moderate support surface micro-environment is crucial for improving enzyme activity. Finally, the immobilized lipase was used for the production of vitamin A palmitate. The immobilized lipase can be reused for up to 18 times with a conversion rate above 90% for 12 h in a 3 L bioreactor. Research highlights An efficient immobilization protocol on polyurethane foam was developed Polyethyleneimine and acetic acid were used to regulate the micro-environment concurrently The activity of lipase immobilized on PUF-HCL-AA/PEI was improved by 2.41 times Immobilized lipase exhibited excellent operational stability for vitamin A palmitate synthesis.

Cellular and metabolic engineering of oleaginous yeast Yarrowia lipolytica for bioconversion of hydrophobic substrates into high-value products

The non-conventional oleaginous yeast Yarrowia lipolytica is able to utilize both hydrophilic and hydrophobic carbon sources as substrates and convert them into value-added bioproducts such as organic acids, extracellular proteins, wax esters, long-chain diacids, fatty acid ethyl esters, carotenoids and omega-3 fatty acids. Metabolic pathway analysis and previous research results show that hydrophobic substrates are potentially more preferred by Y. lipolytica than hydrophilic substrates to make high-value products at higher productivity, titer, rate, and yield. Hence, Y. lipolytica is becoming an efficient and promising biomanufacturing platform due to its capabilities in biosynthesis of extracellular lipases and directly converting the extracellular triacylglycerol oils and fats into high-value products. It is believed that the cell size and morphology of the Y. lipolytica is related to the cell growth, nutrient uptake, and product formation. Dimorphic Y. lipolytica demonstrates the yeast-to-hypha transition in response to the extracellular environments and genetic background. Yeast-to-hyphal transition regulating genes, such as YlBEM1, YlMHY1 and YlZNC1 and so forth, have been identified to involve as major transcriptional factors that control morphology transition in Y. lipolytica. The connection of the cell polarization including cell cycle and the dimorphic transition with the cell size and morphology in Y. lipolytica adapting to new growth are reviewed and discussed. This review also summarizes the general and advanced genetic tools that are used to build a Y. lipolytica biomanufacturing platform.

Biocatalytic esterification of fatty acids using a low-cost fermented solid from solid-state fermentation with Yarrowia lipolytica

This study aimed to evaluate the use of a lyophilized fermented solid (named solid enzymatic preparation, SEP), with lipase activity, as a low-cost biocatalyst for esterification reactions of fatty acids present in acid raw materials for biodiesel synthesis. The SEP was obtained by solid-state fermentation (SSF) of soybean bran using the strain of Yarrowia lipolytica IMUFRJ 50682 and contains the lipases secreted by this yeast. The esterification reaction of ethanol and the predominant fatty acids present in different acid oil sources for biodiesel production (oleic, linoleic, stearic and palmitic acids) was investigated. Oleic acid conversion of above 85% was obtained after 24 h, using 30 wt% of SEP and ethanol/oleic acid molar ratio of 1, at 30 °C, in a reaction medium with and without solvent (n-hexane). Similar results were achieved with stearic (79%), palmitic (82%) and linoleic (90%) acids. The reusability of SEP was investigated over ten successive batches by washing it with different solvents (ethanol, water or n-hexane) between the cycles of ethyl oleate synthesis. Washing with water allowed the SEP to be reused for six cycles maintaining over 80% of the conversion reached in the first cycle. These results show the potential of this biocatalyst to reduce the content of free fatty acids in acid oils for biodiesel synthesis with a potential to be applied in a broad plethora of raw materials.

Yarrowia lipolytica: a beneficious yeast in biotechnology as a rare opportunistic fungal pathogen: a minireview

Yarrowia lipolytica is one of the most studied "non-conventional" yeast species capable of synthesizing a wide group of valuable metabolites, in particular lipases and other hydrolytic enzymes, microbial oil, citric acid, erythritol and γ-decalactone. Processes based on the yeast have GRAS status ("generally recognized as safe") given by Food and Drug Administration. The majority of research communications regarding to Y. lipolytica claim that the yeast species is non-pathogenic. In spite of that, Y. lipolytica, like other fungal species, can cause infections in immunocompromised and critically ill patients. The yeast possess features that facilitate invasion of the host cell (particularly production of hydrolytic enzymes), as well as the protection of the own cells, such as biofilm formation. The aim of this study was to present well-known yeast species Y. lipolytica as a rare opportunistic fungal pathogen. Possible pathogenicity and epidemiology of this yeast species were discussed. Antifungal drugs susceptibility and increasing resistance to azoles in Y. lipolytica yeasts were also presented.

Enzymatic catalysis for sustainable production of high omega-3 triglyceride oil using imidazolium-based ionic liquids

Two different fish oil preparations, namely triglycerides and ethyl esters containing, respectively, 30.02% and 74.38% of omega-3 fatty acids, were employed as the substrates for transesterification. Catalyzed by immobilized lipase using imidazolium-based ionic liquid systems, the total content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the resulting triglyceride reached 63.60% when 4% hydrophobic ionic liquid was used, which was 11.74% higher than that of the triglyceride produced in a solvent-free reaction system. The activation energy of the product (triglyceride-type fish oil) was 173.64 KJ mol-1, which was not significantly different from that of the commercial ethyl ester-type fish oil, so were the other thermal oxidative kinetic parameters. The kinetic parameters depicting the thermal and oxidative stability of the fish oil product provide the basis for industrial processing, storage, and applications.

Synthetic Biology Expands the Industrial Potential of Yarrowia lipolytica

The oleaginous yeast Yarrowia lipolytica is quickly emerging as the most popular non-conventional (i.e., non-model organism) yeast in the bioproduction field. With a high propensity for flux through tricarboxylic acid (TCA) cycle intermediates and biological precursors such as acetyl-CoA and malonyl-CoA, this host is especially well suited to meet our industrial chemical production needs. Recent progress in synthetic biology tool development has greatly enhanced our ability to rewire this organism, with advances in genetic component design, CRISPR technologies, and modular cloning strategies. In this review we investigate recent developments in metabolic engineering and describe how the new tools being developed help to realize the full industrial potential of this host. Finally, we conclude with our vision of the developments that will be necessary to enhance future engineering efforts.

Lipases: An Overview

Lipases are ubiquitous enzymes, widespread in nature. They were first isolated from bacteria in the early nineteenth century, and the associated research continuously increased due to the characteristics of these enzymes. This chapter reviews the main sources, structural properties, and industrial applications of these highly studied enzymes.

Ochratoxin A is degraded by Yarrowia lipolytica and generates non-toxic degradation products

The mycotoxin ochratoxin A (OTA) is a common contaminant of various plant-derived foods and feeds. However, methods for complete decontamination remain to be established. Recently, biological approaches for mycotoxin removal using various species of yeast have been explored. In the present study, we investigated the efficacy of OTA degradation by the yeast Yarrowia lipolytica under various conditions, altering yeast concentration, temperature, pH, and concentration of OTA in order to determine the optimal requirements of this species. At a yeast concentration of 108 cells/ml, the degradation rate was higher than that observed at any other concentration and, after 24 h, the OTA concentration was reduced to almost half of the initial level introduced to the culture. Further, Y. lipolytica cultured at 28 °C showed the highest level of OTA degradation. Similarly, the culture performed optimally at a pH of 4. The initial concentration of OTA also affected the ability of the yeast to degrade OTA, with the level of degradation being the highest when the initial OTA concentration was 0.1 μg/ml. Moreover, we also tested the toxicity of the OTA biodegradation products using HepG2 cells to determine the physiological applicability of this yeast species in the food industry and observed that these products were notably less toxic than non-degraded OTA. Y. lipolytica effectively reduced natural decay incidence of grapes, and had no negative effect to the storage quality of grape fruits. Taken together, these data suggest that Y. lipolytica could be a viable OTA contamination prevention/treatment option and additional research concerning its commercial use is warranted.

Genome mining of fungal lipid-degrading enzymes for industrial applications

Lipases are interesting enzymes, which contribute important roles in maintaining lipid homeostasis and cellular metabolisms. Using available genome data, seven lipase families of oleaginous and non-oleaginous yeast and fungi were categorized based on the similarity of their amino acid sequences and conserved structural domains. Of them, triacylglycerol lipase (patatin-domain-containing protein) and steryl ester hydrolase (abhydro_lipase-domain-containing protein) families were ubiquitous enzymes found in all species studied. The two essential lipases rendered signature characteristics of integral membrane proteins that might be targeted to lipid monolayer particles. At least one of the extracellular lipase families existed in each species of yeast and fungi. We found that the diversity of lipase families and the number of genes in individual families of oleaginous strains were greater than those identified in non-oleaginous species, which might play a role in nutrient acquisition from surrounding hydrophobic substrates and attribute to their obese phenotype. The gene/enzyme catalogue and relevant informative data of the lipases provided by this study are not only valuable toolboxes for investigation of the biological role of these lipases, but also convey potential in various industrial applications.