Effect of roasting on degradation and structural features of polysaccharides in Arabica coffee beans

The degree and nature of polysaccharide degradation at different roasting levels was determined for three Arabica (Coffea arabica) bean varieties. Between 12 and 40% of the bean polysaccharides were degraded depending on the roasting conditions. The thermal stability of the arabinogalactans, (galacto)mannans and cellulose was markedly different. The arabinogalactans and mannans were degraded up to 60 and 36%, respectively, after a dark roast, while cellulose showed negligible evidence of degradation. Roasting led to increased solubility of both the arabinogalactans and (galacto)mannans from the bean but the structural modifications, which accompanied this change in solubility, were different for each polysaccharide. Despite the moderate degradation of the (galacto)mannans, those remaining in the bean after roasting showed no evidence of change to their molecular weight even after a dark roast. In contrast, arabinogalactans were depolymerised after a light roast both by fission of the galactan backbone and loss of arabinose from the sidechains. The recently discovered covalent link between the coffee bean arabinogalactans and protein survived roasting. The glucuronic acid component of the AG was degraded markedly after a dark roast, but approximately 30% of the original content remained as part of the AG polymer. The results show that polysaccharide degradation during roasting is more marked than previously documented, and points to roasting induced changes to the polysaccharides as major factors in the changing physicochemical profile of the coffee bean during processing.     

Effect of polygalacturonase and feruloyl esterase from Aspergillus tubingensis on demucilage and quality of coffee beans

To explore the potential for the application of Aspergillus tubingensis enzyme extract in coffee processing, the effects of crude enzymes on coffee beans were studied. Yields of polygalacturonase and feruloyl esterases obtained from solid-state fermentation using A. tubingensis, with pectin and de-starched wheat bran as carbon sources, were 15.9 U/mL and 2.44 U/mL, respectively. Crude enzyme extracts removed the mucilage of coffee cherries within 3 h, which is substantially more efficient than traditional fermentation. Additionally, the viscosity of coffee mucilage was reduced to 80% by a 3-h treatment with the crude enzyme extract at 50 °C. The titratable acidity and organic acids in coffee beverages were also decreased to half the amounts of those in the traditionally fermented group. The total chlorogenic acid in the green beans decreased to 67.3%; however, a decline of only 14.3% was observed in the traditionally fermented group. On the other hand, chlorogenic acid lactones in the roasted beans were reduced to 63.9%, and a 37.2% decline in the chlorogenic acid content was detected.     

微藻三酰甘油合成途径及其最新研究进展

三酰甘油(triacylglycerols,TAGs)是动物、植物、微生物和微藻细胞主要的储藏性脂类,它可应用于食品、轻工业和生物燃料等方面,是一种新型可再生能源——生物柴油生产的重要原料。与高等油料作物相比,微藻具有光合作用效率高、生长速度快、油脂产量高、不占用农业耕地和适应多种生长环境等优势,是一种潜在的新型生物柴油生产原料。然而,目前人们对有机体,尤其是微藻细胞内TAG合成与积累的分子机制及细胞的代谢调控机制还知之甚少。对TAG合成的一系列重要过程,包括脂肪酸的合成,TAG生物合成的主要途径和旁路途径,以及与TAG合成相关的关键酶和重要基因等进行了综述,特别对微藻细胞中与TAG合成相关的关键基因的最新研究进展进行了总结,旨在更好地了解油脂代谢的调控途径,为最大限度地供应生物柴油的生产原料提供理论基础。     

Robusta coffee beans post-harvest microflora: Lactobacillus plantarum sp. as potential antagonist of Aspergillus carbonarius

Coffee contamination by ochratoxigenic fungi affects both coffee quality as well as coffee price with harmful consequences on the economy of the coffee exporting countries for whom which is their main source of income. Fungal strains were isolated from coffee beans and identified as black Aspergilli. Ochratoxigenic moulds like Aspergillus carbonarius were screened and selected for detailed studies. Also lactic acid bacteria (LAB) were isolated from silage coffee pulp and their antifungal activity was tested on dual-culture agar plate. Ten of the isolated LAB demonstrated antifungal effect against A. carbonarius. API 50 CH and APIZYM were used to perform phenotypic identification. 16S rDNA sequencing was made to confirm the results.     

Determination of the triacylglycerol composition of coffee beans by reverse-phase high-performance liquid chromatography

Reverse-phase HPLC with refractive index and light scattering detectors in isocratic and gradient elution modes, respectively, was applied for the separation of the major triacylglycerols (TAG) in coffee lipids. Twelve TAG species could be identified and determined using a linear gradient of acetonitrile in dichloromethane: dichloroethane. The quantitative evaluation was based on the relative area percentages derived directly from a data-station. The procedure was applied to determine the TAG composition of three types of coffee beans harvested in two coffee producing areas in Brazil and dried by two commonly used procedures. No significant differences in the TAG compositions due to the type, origin and drying procedure were found.     

Cytochemistry and immunolocalisation of polysaccharides and proteoglycans in the endosperm of green Arabica coffee beans

Summary. The major noncellulosic polysaccharides and proteoglycans in the coffee bean (Coffea arabica) cell wall are (galacto)mannans and arabinogalactan proteins. Immunological and chemical probes demonstrated that the mannans and arabinogalactan proteins were located continuously across the width of the cell wall, but that the concentration of different structural epitopes within these polysaccharide types showed considerable spatial variation. For the mannans this was implied by the striated pattern demonstrated by fluctuation of the affinity between the mannan monoclonal antibody BGM C6 and (galacto)mannan. The arabinogalactan proteins labelled by the Yariv reagent and the arabinogalactan protein-specific antibody LM2 appeared to be located in all regions of the wall except the middle lamella, but showed some differences in intensity of labelling. However, the LM6 antibody, specific for (15)--arabinan epitopes, was located only as a compact region adjacent to the cell lumen in the body of the endosperm; though, it did label throughout the wall of epidermal cells. This implied that either some of the more highly arabinosylated arabinogalactan proteins contained contiguous 5-arabinosyl residues or that a rhamnogalacturonan which contained 5-arabinosyl residues as side chains existed in the cell wall. In either case the polymers were very restricted in their distribution. A second category of pectin, a homogalacturonan detected by JIM7, was located only in the middle lamella region. The architecture of the wall, as revealed by resin etching, appeared to reflect the chemical heterogeneity, with three distinct physical zones identifiable in a cross section across a single wall.Correspondence and reprints: Nestlé Research Center, Nestec Ltd., Vers-chez-les-Blanc, P.O. Box 44, 1000 Lausanne 26, Switzerland     

Plant triacylglycerols as feedstocks for the production of biofuels

Triacylglycerols produced by plants are one of the most energy-rich and abundant forms of reduced carbon available from nature. Given their chemical similarities, plant oils represent a logical substitute for conventional diesel, a non-renewable energy source. However, as plant oils are too viscous for use in modern diesel engines, they are converted to fatty acid esters. The resulting fuel is commonly referred to as biodiesel, and offers many advantages over conventional diesel. Chief among these is that biodiesel is derived from renewable sources. In addition, the production and subsequent consumption of biodiesel results in less greenhouse gas emission compared to conventional diesel. However, the widespread adoption of biodiesel faces a number of challenges. The biggest of these is a limited supply of biodiesel feedstocks. Thus, plant oil production needs to be greatly increased for biodiesel to replace a major proportion of the current and future fuel needs of the world. An increased understanding of how plants synthesize fatty acids and triacylglycerols will ultimately allow the development of novel energy crops. For example, knowledge of the regulation of oil synthesis has suggested ways to produce triacylglycerols in abundant non-seed tissues. Additionally, biodiesel has poor cold-temperature performance and low oxidative stability. Improving the fuel characteristics of biodiesel can be achieved by altering the fatty acid composition. In this regard, the generation of transgenic soybean lines with high oleic acid content represents one way in which plant biotechnology has already contributed to the improvement of biodiesel.     

利用基因工程改良植物脂肪酸和提高植物含油量的研究进展

植物脂肪酸和三酰甘油具有重要生理功能以及巨大的食用和工业价值,其生物合成途径较为复杂。近年来,植物脂肪酸和三酰甘油合成代谢途径的研究取得了很大进展,在多种植物中克隆了脂肪酸和三酰甘油合成代谢途径中的关键酶基因,同时发现一些转录因子在调控植物脂肪酸含量和组成中具有重要作用,并在此基础上开展了利用基因工程改良植物脂肪酸和提高植物含油量的研究,取得了一定的进展。以下系统介绍了植物脂肪酸和三酰甘油合成代谢途径中的关键酶基因以及在调控植物脂肪酸含量和组成中具有重要作用的转录因子,综述了基因工程研究所取得的成果,并对其应用前景进行了展望。     

Survey of duckweed diversity in Lake Chao and total fatty acid,triacylglycerol, profiles of representative strains

Lemnaceae (duckweeds) are widely distributed aquatic flowering plants. Their high growth rate, starch content and suitability for bioremediation make them potential feedstock for biofuels. However, few natural duckweed resources have been investigated in China, and there is no information about total fatty acid (TFA) and triacylglycerol (TAG) composition of duckweeds from China. Here, the genetic diversity of a natural duckweed population collected from Lake Chao, China, was investigated using multilocus sequence typing (MLST). The 54 strains were categorised into four species in four genera, representing 12 distinct sequence types. Strains representing Lemna aequinoctialis and Spirodela polyrhiza were predominant. Interestingly, a surprisingly high degree of genetic diversification within L. aequinoctialis was observed. The four duckweed species revealed a uniform fatty acid composition, with three fatty acids, palmitic acid, linoleic acid and linolenic acid, accounting for more than 80% of the TFA. The TFA in biomass varied among species, ranging from 1.05% (of dry weight, DW) for L. punctata and S. polyrhiza to 1.62% for Wolffia globosa. The four duckweed species contained similar TAG contents, 0.02% mg·DW^?1. The fatty acid profiles of TAG were different from those of TFA, and also varied among the four species. The survey investigated the genetic diversity of duckweeds from Lake Chao, and provides an initial insight into TFA and TAG of four duckweed species, indicating that intraspecific and interspecific variations exist in the content and composition of both TFA and TAG in comparison with other studies.     

Effect of long chain fatty acids on triacylglycerol accumulation,fatty acid composition and related gene expression in primary cultured bovine satellite cells

Abstract

This study was conducted to determine the effects of long chain fatty acids (LCFAs) on triacylglycerol (TAG) content, as well as on genes associated with lipid synthesis and fatty acid composition in bovine satellite cells. Both saturated (palmitic and stearic) and unsaturated (oleic and linoleic) fatty acids stimulated the TAG accumulation at a concentration of 100?µM and oleate increased it significantly more than stearate and palmitate. The results revealed that the lipid droplet formation was markedly stimulated by linoleate and oleate at 100?µM. Compared to control, the expressions of adipose triglyceride lipase, carnitine acyltransferase 1 and the fatty acid translocase 36 were upregulated by LCFAs. All the fatty acids also significantly increased diacylglycerol acyltransferase 2 than the untreated control (p?<?0.05). The monounsaturated fatty acids significantly increased (p?<?0.05) in response to oleate and linoleate compared to the control as did the polyunsaturated fatty acids (p?<?0.05), in addition to stearate, linoleate and oleate. In contrast, saturated fatty acids were significantly decreased in the oleate and linoleate-treated groups. The study results contribute to our enhanced understanding of LCFAs’ regulatory roles on the bovine cell lipid metabolism.     

Bioavailability of chlorogenic acids following acute ingestion of coffee by humans with an ileostomy

The intestinal absorption and metabolism of 385 μmol chlorogenic acids following a single intake of 200 mL of instant coffee by human volunteers with an ileostomy was investigated. HPLC-MS³ analysis of 0-24 h post-ingestion ileal effluent revealed the presence of 274 ± 28 μmol of chlorogenic acids and their metabolites accounting for 71 ± 7% of intake. Of the compounds recovered, 78% comprised parent compounds initially present in the coffee, and 22% were metabolites including free and sulfated caffeic and ferulic acids. Over a 24 h period after ingestion of the coffee, excretion of chlorogenic acid metabolites in urine accounted for 8 ± 1% of intake, the main compounds being ferulic acid-4-O-sulfate, caffeic acid-3-O-sulfate, isoferulic acid-3-O-glucuronide and dihydrocaffeic acid-3-O-sulfate. In contrast, after drinking a similar coffee, urinary excretion by humans with an intact colon corresponded to 29 ± 4% of chlorogenic acid intake [23]. This difference was due to the excretion of higher levels of dihydroferulic acid and feruloylglycine together with sulfate and glucuronide conjugates of dihydrocaffeic and dihydroferulic acids. This highlights the importance of colonic metabolism. Comparison of the data obtained in the current study with that of Stalmach et al. [23] facilitated elucidation of the pathways involved in post-ingestion metabolism of chlorogenic acids and also helped distinguish between compounds absorbed in the small and the large intestine.     

Partial purification and characterization of the lipoxygenase from grains of Hordeum distichum

Lipoxygenase activities in ungerminated and germinating barley grains were found to be associated exclusively with the embryos. A lipoxygenase was extracted from ungerminated embryos and partially purified by fractional precipitation with ammonium sulfate and gel-filtration. Both the crude extracts and the purified preparation appeared to contain only a fatty acid type lipoxygenase which mainly converted linolele acid to 9-hydroperoxy, trans-10, cis-12-octadecadienoic acid. The purified enzyme was inhibited by its own products, hydroperoxides, but not by 1 mM cyanide, EDTA, Hg²⁺ or Cu²⁺.     

Microencapsulation of Linoleic Acid with Low- and High-molecular-weight Components of Soluble Soybean Polysaccharide and Its Oxidation Process

Soluble soybean polysaccharide (SSPS) was fractionated into its low- (LMW) and high-molecular-weight (HMW) components to test their antioxidative and emulsifying properties. Linoleic acid was emulsified with an aqueous solution of SSPS, HMW, a mixture of LMW or HMW with maltodextrin, or maltodextrin alone. The emulsions prepared with SSPS, HWM and the mixture of HMW with maltodextrin were stable. These emulsions were spay-dried to produce microcapsules. The encapsulated linoleic acid was oxidized at 37°C and at various levels of relative humidity. Linoleic acid encapsulated with the mixture of LMW with maltodextrin or HMW was stable to oxidation, and this stability increased as the weight fraction of LMW in the mixture was increased. The LMW components also had high DPPH-radical scavenging activity. These results indicate that LMW played an important role in suppressing or retarding the oxidation of linoleic acid encapsulated with SSPS. The oxidative stability of linoleic acid encapsulated with a mixture of the LMW and HMW components was high at low and high relative humidity, but not at intermediate levels of relative humidity.     

Responses of triacylglycerol synthesis in Skeletonema marinoi to nitrogen and phosphate starvations

Skeletonema marinoi is one of the most widespread marine planktonic diatoms in temperate coastal regions and sometimes can form massive blooms. Yet, the molecular mechanisms of triacylglycerol (TAG) synthesis in nutrient-deficient conditions for this species are still unknown. This study aimed to investigate how the TAG biosynthetic pathway of S. marinoi reacts to the culture age and nitrogen (N) or phosphorus (P) deficiency at molecular levels. Meanwhile, we also described the physiological and biochemical changes of S. marinoi in response to N or P starvation over time. To obtain reliable qRT-PCR data, six putative reference genes were identified for assessing expression stability using geNorm and BestKeeper software, and Actin exhibited the most stable expression across 45 tested S. marinoi samples. We found that the expression of TAG biosynthesis-related genes and ACCase enzyme activity varied in response to the different nutrient conditions and culture age. Taken together, we speculated that the capacity of TAG biosynthesis in S. marinoi is induced by N or P stress, and increases with culture age. Furthermore, TAG biosynthesis appears to respond more strongly to P deficiency than to N deficiency. Our study provides important insights into how diatoms regulate the TAG biosynthetic pathway when stressed by nutrient limitation. Besides, the data obtained from this study also provide useful clues for further exploring genes that can be used for metabolic engineering to enhance lipid production.     

Comparison of CO2 and bicarbonate as inorganic carbon sources for triacylglycerol and starch accumulation in Chlamydomonas reinhardtii

Microalgae are capable of accumulating high levels of lipids and starch as carbon storage compounds. Investigation into the metabolic activities involved in the synthesis of these compounds has escalated since these compounds can be used as precursors for food and fuel. Here, we detail the results of a comprehensive analysis of Chlamydomonas reinhardtii using high or low inorganic carbon concentrations and speciation between carbon dioxide and bicarbonate, and the effects these have on inducing lipid and starch accumulation during nitrogen depletion. High concentrations of CO₂ (5%; v/v) produced the highest amount of biofuel precursors, transesterified to fatty acid methyl esters, but exhibited rapid accumulation and degradation characteristics. Low CO₂ (0.04%; v/v) caused carbon limitation and minimized triacylglycerol (TAG) and starch accumulation. High bicarbonate caused a cessation of cell cycling and accumulation of both TAG and starch that was more stable than the other experimental conditions. Starch accumulated prior to TAG and then degraded as maximum TAG was reached. This suggests carbon reallocation from starch‐based to TAG‐based carbon storage. Biotechnol. Bioeng. 2013; 110: 87–96. © 2012 Wiley Periodicals, Inc.     

The pathway of triacylglycerol synthesis through phosphatidylcholine in Arabidopsis produces a bottleneck for the accumulation of unusual fatty acids in transgenic seeds

Engineering of oilseed plants to accumulate unusual fatty acids (FAs) in seed triacylglycerol (TAG) requires not only the biosynthetic enzymes for unusual FAs but also efficient utilization of the unusual FAs by the host-plant TAG biosynthetic pathways. Competing pathways of diacylglycerol (DAG) and subsequent TAG synthesis ultimately affect TAG FA composition. The membrane lipid phosphatidylcholine (PC) is the substrate for many FA-modifying enzymes (desaturases, hydroxylases, etc.) and DAG can be derived from PC for TAG synthesis. The relative proportion of PC-derived DAG versus de novo synthesized DAG utilized for TAG synthesis, and the ability of each pathway to utilize unusual FA substrates, are unknown for most oilseed plants, including Arabidopsis thaliana. Through metabolic labeling experiments we demonstrate that the relative flux of de novo DAG into the PC-derived DAG pathway versus direct conversion to TAG is ～14/1 in wild-type Arabidopsis. Expression of the Ricinus communis FA hydroxylase reduced the flux of de novo DAG into PC by ～70%. Synthesis of TAG directly from de novo DAG did not increase, resulting in lower total synthesis of labeled lipids. Hydroxy-FA containing de novo DAG was rapidly synthesized, but it was not efficiently accumulated or converted to PC and TAG, and appeared to be in a futile cycle of synthesis and degradation. However, FA hydroxylation on PC and conversion to DAG allowed some hydroxy-FA to accumulate in sn-2 TAG. Therefore, the flux of DAG through PC represents a major bottleneck for the accumulation of unusual FAs in TAG of transgenic Arabidopsis seeds.     

The effect of beverage preparation method on aluminium content in coffee infusions

Seven types of coffee were prepared by four methods. Three of them – simple coffee infusion, preparation in ibrick and moka pot – are very often used to prepare coffee at home. The fourth one – a single-cup filter is typical for Vietnam. Cookware used for each method was made from glass, aluminium, stainless steel and two types of alloys. Amounts of Al leaching to coffee infusions were determined. On average, the highest amount of Al was in coffee infusions brewed in aluminium single-cup filter, and the lowest in infusions prepared by simple extraction. Other brewing methods in combination with different tool materials resulted in similar Al content. The type of brewing method significantly influences the Al content in final infusion. Aluminium content varies in infusions in relation to the method of choice, especially when using single-cup filter. Despite the fact that coffee is considered to be a poor source of Al for humans, in some cases, Al content in infusions can even reach the values reported for tea infusions.