Recent Progress in Microalgal Squalene Production and Its Cosmetic Application

Enhanced oxidative stability of deuterated squalene: the impact of labelling extent on chemical resilience

The extent to which deuteration affects the oxidative stability of squalene, a nutrient and a commonly-used ingredient in cosmetics and vaccine adjuvants, has been quantified as a function of the extent of labelling. The formation of comedogenic peroxides was inhibited by levels of overall deuteration as low as 19%.

Valorization of Carapa guianensis Aubl. seeds treated by compressed n-propane

This study evaluated the oil content obtained from andiroba seeds by pressurized n-propane at different conditions of temperature (25, 35, and 45 °C) and pressure (40, 60, and 80 bar), and conventional extraction technique using n-hexane as the solvent. Kinetic extraction curves were fitted using Sovová's mathematical model. The chemical characterization of the oil was reported as well as the protein content in the extraction by-product. Pressurized extractions conducted at 25 °C provided the highest oil recovery (~45 wt%) from the seeds. The increase in pressure at 25 ºC favored obtaining oil with higher Stigmasterol contents, however, the Squalene content was higher in the oil obtained at 40 bar. The oils with the highest concentration phenolic compounds and antioxidant activity were obtained at 80 bar. Extraction with n-propane provided oils with higher levels of phenolic compounds, however, with antioxidant activity similar to conventional extraction. For all evaluated extractions, the product showed a predominance of oleic and palmitic acids, with similar values of oxidative stability. The extraction of the by-product with the highest soluble protein content was obtained under mild processing conditions (25 °C and 40 bar) with n-propane.

Remodeling the Homologous Recombination Mechanism of Yarrowia lipolytica for High-Level Biosynthesis of Squalene

Squalene is a high-value antioxidant with many commercial applications. The use of microbial cell factories to produce squalene as an alternative to plant and animal extracts could meet increasing market demand. Yarrowia lipolytica is an excellent host for squalene production due to its high levels of acetyl-CoA and a hydrophobic environment. However, the need for precise and complicated gene editing has hindered the industrialization of this strain. Herein, the rapid construction of a strain with high squalene production was achieved by enhancing the homologous recombination efficiency in Y. lipolytica. First, remodeling of the homologous recombination efficiency resulted in a 10-fold increase in the homologous recombination rate. Next, the whole mevalonate pathway was integrated into the chromosome to enhance squalene production. Then, a higher level of squalene accumulation was achieved by increasing the level of acetyl coenzyme A and regulating the downstream steroid synthesis pathway. Finally, the squalene production reached 35 g/L after optimizing the fermentation conditions and performing a fed-batch culture in a 5 L jar fermenter. This is the highest squalene production ever reported to date by de novo biosynthesis without adding any inhibitors, paving a new path toward the industrial production of squalene and its downstream products.

The Nitrogen Content in the Fruiting Body and Mycelium of Pleurotus Ostreatus and Its Utilization as a Medium Component in Thraustochytrid Fermentation

Following the idea of a circular bioeconomy, the use of side streams as substitutes for cultivation media (components) in bioprocesses would mean an enormous economic and ecological advantage. Costly compounds in conventional media for the production of the triterpene squalene in thraustochytrids are the main carbon source and complex nitrogen sources. Among other side streams examined, extracts from the spent mycelium of the basidiomycete Pleurotus ostreatus were best-suited to acting as alternative nitrogen sources in cultivation media for thraustochytrids. The total nitrogen (3.76 ± 0.01 and 4.24 ± 0.04%, respectively) and protein (16.47 ± 0.06 and 18.57 ± 0.18%, respectively) contents of the fruiting body and mycelium were determined. The fungal cells were hydrolyzed and extracted to generate accessible nitrogen sources. Under preferred conditions, the extracts from the fruiting body and mycelium contained 73.63 ± 1.19 and 89.93 ± 7.54 mM of free amino groups, respectively. Cultivations of Schizochytrium sp. S31 on a medium using a mycelium extract as a complex nitrogen source showed decelerated growth but a similar squalene yield (123.79 ± 14.11 mg/L after 216 h) compared to a conventional medium (111.29 ± 19.96 mg/L, although improvable by additional complex nitrogen source).

Squalene production under oxygen limitation by Schizochytrium sp. S31 in different cultivation systems

The triterpene squalene is widely used in the food, cosmetics and pharmaceutical industries due to its antioxidant, antistatic and anti-carcinogenic properties. It is usually obtained from the liver of deep sea sharks, which are facing extinction. Alternative production organisms are marine protists from the family Thraustochytriaceae, which produce and store large quantities of various lipids. Squalene accumulation in thraustochytrids is complex, as it is an intermediate in sterol biosynthesis. Its conversion to squalene 2,3-epoxide is the first step in sterol synthesis and is heavily oxygen dependent. Hence, the oxygen supply during cultivation was investigated in our study. In shake flask cultivations, a reduced oxygen supply led to increased squalene and decreased sterol contents and yields. Oxygen-limited conditions were applied to bioreactor scale, where squalene accumulation and growth of Schizochytrium sp. S31 was determined in batch, fed-batch and continuous cultivation. The highest dry matter (32.03 g/L) was obtained during fed-batch cultivation, whereas batch cultivation yielded the highest biomass productivity (0.2 g/L*h-1). Squalene accumulation benefited from keeping the microorganisms in the growth phase. Therefore, the highest squalene content of 39.67 ± 1.34 mg/g was achieved by continuous cultivation (D = 0.025 h-1) and the highest squalene yield of 1131 mg/L during fed-batch cultivation. Volumetric and specific squalene productivity both reached maxima in the continuous cultivation at D = 0.025 h-1 (6.94 ± 0.27 mg/L*h-1 and 1.00 ± 0.03 mg/g*h-1, respectively). Thus, the choice of a suitable cultivation method under oxygen-limiting conditions depends heavily on the process requirements. KEY POINTS: • Measurements of respiratory activity and backscatter light of thraustochytrids • Oxygen limitation increased squalene accumulation in Schizochytrium sp. S31 • Comparison of different cultivation methods under oxygen-limiting conditions.

Plant-derived squalene supplementation improves growth performance and alleviates acute oxidative stress-induced growth retardation and intestinal damage in piglets

Piglets are particularly susceptible to oxidative stress, which causes inferior growth performance and intestinal damage. Squalene (SQ), a natural bioactive substance enriched in shark liver oil, shows excellent antioxidant properties and can currently be obtained at a low cost from deodorizer distillate during the production of plant oil. This study aimed to evaluate the effects of plant-derived SQ supplementation on the growth performance of piglets and explore the beneficial roles of SQ against oxidative stress and intestinal injury in diquat-challenged piglets. Forty piglets were randomly divided into five groups and fed a basal diet supplemented with SQ at 0, 500, 1000, or 2000 mg/kg for 5 weeks. Acute oxidative stress was induced in the piglets with diquat (10 mg/kg BW) at the fourth week of the experiment, followed by a 7-d recovery period. Results showed that before the diquat challenge, SQ supplementation significantly improved growth performance (average daily gain and feed conversion ratio) and serum antioxidant status, and after the diquat challenge, SQ supplementation significantly mitigated diquat-induced growth arrest, intestinal villous atrophy, intestinal epithelial cell apoptosis, intestinal hyperpermeability, and deficiency of intestinal epithelial tight junction proteins (zonula occludens-1, occludin, and claudin-3). Under oxidative stress induced by diquat, SQ supplementation consistently improved the antioxidant status of the small intestine, liver, and muscle. In vitro, SQ was shown to alleviate hydrogen peroxide (H2O2)-induced increase of the levels of intracellular reactive oxygen species and apoptosis of porcine intestinal epithelial cells. Taken together, SQ supplementation improves growth performance and effectively alleviates acute oxidative stress-induced growth retardation and intestinal injury via improving antioxidant capacity in piglets. Our findings may provide an efficient strategy for alleviating oxidative stress-induced inferior growth performance and intestinal damage in piglets.

Extraction from different parts of Citrus maxima flowers using ultrasound as an aid and study of their composition and function

Ultrasonic assisted extraction is frequently referred to as a green environmental protection method. The flower of Citrus maxima (FCM) has been used as a health tea drink in China, although the tea drink lacks clear compound composition identification and functional research. In order to fully use Citrus fruit by-products and further explore the functional features of FCM, this paper isolated, identified, and assessed the chemical compounds in the petals, stems, styles, receptacles, stamens, and buds of FCM extract. There are 88 compounds were recovered, including 23 compounds in the bud, 21 compounds in the petal, 19 compounds in the stem, 11 compounds in the receptacle, 20 compounds in the stamen, and 13 compounds in the style. Antioxidant experiments revealed that the FCM's various compounds had observable impacts in scavenging free radicals (38.44%-58.35%). The aforementioned study demonstrates that the pomelo by-products were developed into useful components using ultrasonic aided extraction technique. FCM has flavor-rich compounds that make it suited for use as an antioxidant tea beverage and offers practical suggestions for preparing healthy products.

Antioxidant properties of lipid concomitants in edible oils: A review

Edible oils are indispensable for human life, providing energy and necessary fatty acids. Nevertheless, they are vulnerable to oxidation via a number of different mechanisms. Essential nutrients deteriorate as well as toxic substances are produced when edible oils are oxidized; thus, they should be retarded wherever possible. Lipid concomitants have a strong antioxidant capacity and are a large class of biologically active chemical substances in edible oils. They have shown remarkable antioxidant properties and were documented to improve the quality of edible oils in varied ways. An overview of the antioxidant properties of the polar, non-polar, and amphiphilic lipid concomitants present in edible oils is provided in this review. Interactions among various lipid concomitants and the probable mechanisms are also elucidated. This review may provide a theoretical basis and practical reference for food industry practitioners and researchers to understand the underlying cause of variations in the quality of edible oils.

Biosynthesis and the Transcriptional Regulation of Terpenoids in Tea Plants (Camellia sinensis)

Terpenes, especially volatile terpenes, are important components of tea aroma due to their unique scents. They are also widely used in the cosmetic and medical industries. In addition, terpene emission can be induced by herbivory, wounding, light, low temperature, and other stress conditions, leading to plant defense responses and plant-plant interactions. The transcriptional levels of important core genes (including HMGR, DXS, and TPS) involved in terpenoid biosynthesis are up- or downregulated by the MYB, MYC, NAC, ERF, WRKY, and bHLH transcription factors. These regulators can bind to corresponding cis-elements in the promoter regions of the corresponding genes, and some of them interact with other transcription factors to form a complex. Recently, several key terpene synthesis genes and important transcription factors involved in terpene biosynthesis have been isolated and functionally identified from tea plants. In this work, we focus on the research progress on the transcriptional regulation of terpenes in tea plants (Camellia sinensis) and thoroughly detail the biosynthesis of terpene compounds, the terpene biosynthesis-related genes, the transcription factors involved in terpene biosynthesis, and their importance. Furthermore, we review the potential strategies used in studying the specific transcriptional regulation functions of candidate transcription factors that have been discriminated to date.