Enzymatic synthesis and modification of structured phospholipids: recent advances in enzyme preparation and biocatalytic processes

Marine Animal Co-Products-How Improving Their Use as Rich Sources of Health-Promoting Lipids Can Foster Sustainability

Marine lipids are recognized for their-health promoting features, mainly for being the primary sources of omega-3 fatty acids, and are therefore critical for human nutrition in an age when the global supply for these nutrients is experiencing an unprecedent pressure due to an ever-increasing demand. The seafood industry originates a considerable yield of co-products worldwide that, while already explored for other purposes, remain mostly undervalued as sustainable sources of healthy lipids, often being explored for low-value oil production. These co-products are especially appealing as lipid sources since, besides the well-known nutritional upside of marine animal fat, which is particularly rich in omega-3 polyunsaturated fatty acids, they also have interesting bioactive properties, which may garner them further interest, not only as food, but also for other high-end applications. Besides the added value that these co-products may represent as valuable lipid sources, there is also the obvious ecological upside of reducing seafood industry waste. In this sense, repurposing these bioresources will contribute to a more sustainable use of marine animal food, reducing the strain on already heavily depleted seafood stocks. Therefore, untapping the potential of marine animal co-products as valuable lipid sources aligns with both health and environmental goals by guaranteeing additional sources of healthy lipids and promoting more eco-conscious practices.

Transesterification of phosphatidylcholine with DHA-rich algal oil using immobilized Candida antarctica lipase B to produce DHA-phosphatidylcholine

Docosahexaenoic acid (DHA) enriched with phospholipids (PLs) (DHA-PLs) is a type of structured PL with good physicochemical and nutritional properties. Compared to PLs and DHA, DHA-PLs has higher bioavailability and structural stability and many nutritional benefits. To improve the enzymatic synthesis of DHA-PLs, this study investigated the preparation of phosphatidylcholine (PC) enriched with DHA (DHA-PC) via enzymatic transesterification of algal oil, which is rich in DHA-triglycerides, using immobilized Candida antarctica lipase B (CALB). The optimized reaction system incorporated 31.2% DHA into the acyl chain of PC and converted 43.6% PC to DHA-PC within 72 h at 50 °C, 1:8 PC: algal oil mass ratio, 25% enzyme load (based on total substrate mass), and 0.02 g/mL molecular sieve concentration. Consequently, the side reactions of PC hydrolysis were effectively suppressed and products with high PC content (74.8%) were produced. Molecular structure analysis showed that exogenous DHA was specifically incorporated into the sn-1 site of the PC by immobilized CALB. Furthermore, the evaluation of reusability with eight cycles showed that the immobilized CALB had good operational stability in the present reaction system. Collectively, this study demonstrated the applicability of immobilized CALB as a biocatalyst for synthesizing DHA-PC and provided an improved enzyme-catalyzed method for future DHA-PL synthesis.

The ubiquitin-proteasome system in melanin metabolism

BACKGROUND

The ubiquitin-proteasome system (UPS) is a highly conserved way of regulating intracellular protein balance. UPS mediates proteolysis and disruption of variation or misfolding, while finely regulating proteins involved in differentiation and other biological processes.

AIMS

The aim of this review is to systematically introduce UPS as a key regulator of melanin metabolism.

METHODS

Systematic search and retrospective review were performed on the published data.

RESULTS

Melanocyte-inducing transcription factor (MITF) is a substrate of the ubiquitin ligase VCHL1 and acts as a transcription factor to regulate the expression of key enzymes in melanin synthesis such as tyrosinase (TYR). The rate-limiting enzyme TYR is modified by the ubiquitin ligase Hrd1 during melanosynthesis. Melanin itself is also regulated by multiple ubiquitin ligases including Fbp1 and Vhl. By regulating the ubiquitination modification to target each link of melanin synthesis, it plays an important role in correcting the disorder of melanin metabolism. A number of chemical agents have been proven to inhibit the activity of ubiquitin ligase.

CONCLUSIONS

Drugs targeting E3 ligase and deubiquitinating enzymes have great potential in the treatment of melanin metabolism disorders.

Acidolysis of phospholipids with medium-chain fatty acids over M-SBA-15 (M = Zn, Al) silicas as efficient solid catalysts

BACKGROUND

Efficient and sustainable production of structured phospholipids (SPLs) enriched in medium-chain fatty acids (MCFAs) in a heterogeneous manner is crucial for their potential applications in functional foods and drugs. Herein, for the first time, Zn- and Al-incorporated SBA-15 silicas were prepared by the coprecipitation method and further researched for catalytic synthesis of MCFA-enriched SPLs through acidolysis reaction of natural phospholipids with capric or caprylic acid.

RESULTS

The as-prepared Zn- and Al-incorporated SBA-15 samples exhibited superior catalytic activities under mild experimental conditions (50 °C, 6 h) to commercial homogeneous Lewis acids and benchmark enzymes. Correspondingly, the capric acid and caprylic acid incorporations were respectively achieved up to ~40.25 ± 0.40% (or 35.08 ± 0.09%) and 37.26 ± 0.38% (or 33.02 ± 0.13%) for Zn- (or Al-) incorporated SBA-15 catalyst. Moreover, various methods such as scanning electron microscopy with energy-dispersive X-ray spectrometry, ultraviolet-visible diffuse reflectance spectroscopy and pyridine-Fourier transform infrared spectroscopy were utilized to characterize the two catalysts in order to elucidate the possible structure-performance relationship. Accordingly, the above-mentioned satisfactory results are most probably due to the well-ordered mesostructures and large amounts of active Lewis acid sites existing in the investigated materials. Noticeably, the two catalysts featured good separation and excellent recyclability as well.

CONCLUSION

The Zn- and Al-incorporated SBA-15 catalysts studied in this work might shed light on novel, sustainable and economic alternatives for effective SPL production to diminish the applications of conventional homogeneous catalysts and biocatalysts in food industries. © 2022 Society of Chemical Industry.

Progress & Prospect of Enzyme-Mediated Structured Phospholipids Preparation

In recent years, structured phospholipids (SPLs), which are modified phospholipids (PLs), have attracted more attention due to their great potential for application in the field of pharmacy, food, cosmetics, and health. SPLs not only possess enhanced chemical, physical and nutritional properties, but also present superior bioavailability in comparison with other lipid forms, such as triacylglycerols, which make SPLs become more competitive carriers to increase the absorption of the specific fatty acids in the body. Compared with chemical-mediated SPLs, the process of enzyme-mediated SPLs has the advantages of high product variety, high substrate selectivity, and mild operation conditions. Both lipases and phospholipases can be used in the enzymatic production of SPLs, and the main reaction type contains esterification, acidolysis, and transesterification. During the preparation, reaction medium, acyl migration, water content/activity, substrates and enzymes, and some other parameters have significant effects on the production and purity of the desired PLs products. In this paper, the progress in enzymatic modification of PLs over the last 20 years is reviewed. Reaction types and characteristic parameters are summarized in detail and the parameters affecting acyl migration are first discussed to give the inspiration to optimize the enzyme-mediated SPLs preparation. To expand the application of enzyme-mediated SPLs in the future, the prospect of further study on SPLs is also proposed at the end of the paper.

Rational Design of Phospholipase D to Improve the Transphosphatidylation Activity for Phosphatidylserine Synthesis

Phosphatidylserine (PS) has been widely used in the fields of food and medicine, among others, owing to its unique chemical structure and health benefits. However, the phospholipase D (PLD)-mediated enzymatic production of PS remains a challenge due to the low transphosphatidylation activity of PLD. Therefore, in the present study, we designed a maltose-binding protein (MBP) tag and a PLD co-expression method to achieve the expression of soluble PLD in Escherichia coli. A "reconstruct substrate pocket" strategy was then proposed based on the catalytic mechanism and molecular dynamics simulation, expanding the substrate pocket and manipulating the coordination of l-Ser within the active site. The best mutant (Sr_MBPPLD^Mu6) exhibited a 2.04-fold higher transphosphatidylation/hydrolysis ratio than the wild-type Furthermore, under optimal conditions, Mu₆ produced 58.6 g/L PS with 77.2% conversion, within 12 h on a 3 L scale, which demonstrates the potential of the proposed method for industrial application.

Phospholipids (PLs) know-how: exploring and exploiting phospholipase D for its industrial dissemination

Owing to their numerous nutritional and bioactive functions, phospholipids (PLs), which are major components of biological membranes in all living organisms, have been widely applied as nutraceuticals, food supplements, and cosmetic ingredients. To date, PLs are extracted solely from soybean or egg yolk, despite the diverse market demands and high cost, owing to a tedious and inefficient manufacturing process. A microbial-based manufacturing process, specifically phospholipase D (PLD)-based biocatalysis and biotransformation process for PLs, has the potential to address several challenges associated with the soybean- or egg yolk-based supply chain. However, poor enzyme properties and inefficient microbial expression systems for PLD limit their wide industrial dissemination. Therefore, sourcing new enzyme variants with improved properties and developing advanced PLD expression systems are important. In the present review, we systematically summarize recent achievements and trends in the discovery, their structural properties, catalytic mechanisms, expression strategies for enhancing PLD production, and its multiple applications in the context of PLs. This review is expected to assist researchers to understand current advances in this field and provide insights for further molecular engineering efforts toward PLD-mediated bioprocessing.

Characteristics and emulsifying properties of structured phospholipids from palm pressed fiber and omega-3 fatty acid concentrates from by-products of fish processing by enzymatic acidolysis

The synthesis of structured phospholipids (SPLs) containing ω-3 fatty acids was carried out through enzymatic acidolysis reactions using lipase from Rhizomucor miehei between palm pressed fiber phospholipids (PPF PL) with four ω-3 fatty acid concentrates as different acyl sources. The purity of SPLs increased compared to original PPF PLs. The degree of ω-3 fatty acid incorporation to the SPLs was different that depended on the sources of acyl. The highest degree of incorporation was in PE (phosphatidylethanolamine). The phenomenon of acyl migration of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) was found from the sn-1 to the sn-2 position of the PE. This acyl migration occurred at all four SPLs. Modification of PLs made better emulsifying properties for oil in water emulsion system, compared to PPF PL. The increase in the HLB (hydrophilic-lipophilic balance) value, EAI (emulsifying activity index), and ESI (emulsion stability index) of SPLs compared to PPF PL was supposed to relate to an increase in polarity. The composition of more polar PLs (PC/phosphatidylcholine, PE, PG/phosphatidylglycerol, and PA/phosphatidic acid) in the four SPLs is higher than that of PPF PL. The sources of acyl also affected the emulsifying properties of four SPLs.

Interactions of fungal phospholipase Lecitase ultra with phospholipid Langmuir monolayers - Search for substrate specificity and structural factors affecting the activity of the enzyme

Inoculation of selected microbial species into the soils is one of the most effective means of bioremediation of soils polluted by persistent organic pollutants as well as of biocontrol of plant pests. However, this procedure turns out frequently to be ineffective due to the membrane-destructive enzymes secreted to the soil by the autochthonous microorganisms. Especial role play here phospholipases and among them phospholipase A1 (PLA1), Therefore, to explain the interactions of microbial membranes and PLA1 at molecular level and to find the correlation between the composition of the membrane and its resistance to PLA1 action we applied phospholipid Langmuir monolayers as model microbial membranes. As a representative soil extracellular PLA1 we applied Lecitase ultra which is a commercially available hybrid enzyme of PLA1 activity. With the application of specific sn1-ether-sn2-ester phospholipids we proved that Lecitase ultra has solely PLA1 activity; thus, can be applied as an effective model of soil PLA1s. Our studies proved that this enzyme has vast substrate specificity and can hydrolyze structural phospholipids regardless the structure of their polar headgroup. It turned out that the hydrolysis rate was controlled by the condensation of the model membranes. These built of the phospholipids with long saturated fatty acid chains were especially resistant to the action of this enzyme, whereas these formed by the 1-saturated-2-unsaturated-sn-glycero-3-phospholipids were readily degraded. Regarding the polar headgroup we proposed the following row of substrate preference of Lecitase ultra: phosphatidylglycerols > phosphatidylcholines > phosphatidylethanolamines > cardiolipins.

Construction of a Super-Folder Fluorescent Protein-Guided Secretory Expression System for the Production of Phospholipase D in Bacillus subtilis

Phospholipids (PLs) are one of the main ingredients in food and nutraceutical, cosmetics, agriculture, and pharmaceutical products. Phospholipase D (PLD) is a crucial enzyme for the biocatalytic synthesis or modification of PLs. Here, to prepare PLD more efficiently, we constructed a PLD expression and secretion system in Bacillus subtilis and developed an environmentally friendly reaction system. A nonclassical secretory pathway where a super-folder green fluorescent protein plays as an N-terminal guide protein was introduced. This expression system can not only achieve rapid screening of high-level expression strains but can also achieve the secretion of the target proteins. Under optimal fermentation conditions, the enzyme activity of the culture medium was 0.35 U/mL, which was 2.05-fold that of the Sec secretion pathway strains. Meanwhile, the effects of several organic solvents in the biphasic reaction media were compared. The results showed that when using cyclopentyl methyl ether as the organic phase, the final conversion rate reached 96.9%. It has shown good application potential in the synthesis of phosphatidylserine, laid the foundation for the synthesis and application of other rare and high-value PLs, and provided a reference for the production of other biocatalysts.

Enzymatic modification to produce health-promoting lipids from fish oil, algae and other new omega-3 sources: A review

Lipases are a versatile class of enzymes that have aroused great interest in the food and pharmaceutical industries due to their ability to modify and synthesize new lipids for functional foods. Omega-3 polyunsaturated fatty acids (omega-3 PUFAs), such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have shown important biological functions promoting human health, especially in the development and maintenance of brain function and vision. Lipases allow selective production of functional lipids enriched in omega-3 PUFAs and are unique enzymatic tools to improve the natural composition of lipids and provide specific bioactivities. This review comprises recent research trends on the enzymatic production of bioactive, structured lipids with improved nutritional characteristics, using new enzymatic processing technologies in combination with novel raw materials, including microalgal lipids and new seed oils high in omega-3 fatty acids. An extensive number of lipase applications in the synthesis of health-promoting lipids enriched in omega-3 fatty acids by enzymatic modification is reviewed, considering the main advances in recent years for production of ethyl esters, 2-monoacylglycerols and structured triglycerides and phospholipids with omega-3 fatty acids, in order to achieve bioactive lipids as new foods and drugs.

Cell-free synthesis of functional phospholipase A1 from Serratia sp

BACKGROUND

Phospholipase A1 is an enzyme that hydrolyzes phospholipids at the sn-1 position. It has potential applications across diverse fields including food, pharmaceutical, and biofuel industries. Although there has been increasing interest in the use of phospholipase A1 for degumming of plant oils during biodiesel production, production of recombinant phospholipase A1 has been hampered by low efficiency of gene expression and its toxicity to the host cell.

RESULTS

While expression of phospholipase A1 in Escherichia coli resulted in extremely low productivity associated with inhibition of transformed cell growth, drastically higher production of functional phospholipase A1 was achieved in a cell-free protein synthesis system where enzyme expression is decoupled from cell physiology. Compared with expression in E. coli, cell-free synthesis resulted in an over 1000-fold higher titer of functional phospholipase A1. Cell-free produced phospholipase A1 was also used for successfully degumming crude plant oil.

CONCLUSIONS

We demonstrate successful production of Serratia sp. phospholipase A1 in a cell-free protein synthesis system. Including the phospholipase A1 investigated in this study, many industrial enzymes can interfere with the regular physiology of cells, making cellular production of them problematic. With the experimental results presented herewith, we believe that cell-free protein synthesis will provide a viable option for rapid production of important industrial biocatalysts.