Production Of Esters Research Articles

Isolation, identification, and tolerance analysis of yeast during the natural fermentation process of Sidamo coffee beans.

Yeast, which plays a pivotal role in the brewing, food, and medical industries, exhibits a close relationship with human beings. In this study, we isolated and purified 60 yeast strains from the natural fermentation broth of Sidamo coffee beans to screen for indigenous beneficial yeasts. Among them, 25 strains were obtained through morphological characterization on nutritional agar medium from Wallerstein Laboratory (WL), with molecular biology identifying Saccharomyces cerevisiae strain YBB-47 and the remaining 24 yeast strains identified as Pichia kudriavzevii. We investigated the fermentation performance, alcohol tolerance, SO2 tolerance, pH tolerance, sugar tolerance, temperature tolerance, ester production capacity, ethanol production capacity, H2S production capacity, and other brewing characteristics of YBB-33 and YBB-47. The results demonstrated that both strains could tolerate up to 3% alcohol by volume at a high sucrose mass concentration (400g/L) under elevated temperature conditions (40 ℃), while also exhibiting a remarkable ability to withstand an SO2 mass concentration of 300g/L at pH 3.2. Moreover, S. cerevisiae YBB-47 displayed a rapid gas production rate and strong ethanol productivity. whereas P. kudriavzevii YBB-33 exhibited excellent alcohol tolerance. Furthermore, this systematic classification and characterization of coffee bean yeast strains from the Sidamo region can potentially uncover additional yeasts that offer high-quality resources for industrial-scale coffee bean production.

Environmental microbiota and its influence on microbial succession and metabolic profiles in baijiu fermentation across three distinct-age workshops

The fermentation of Baijiu is profoundly influenced by environmental microbiota, but the exact origins and the specific impacts of these microbes are not entirely understood. To address this issue, we used reverse-analysis to comprehensively map the environmental sources and reveal their pivotal role in shaping microbial succession and metabolic variations across three workshops of different ages. We initially discovered that these workshops exhibited unique microbial succession and metabolic profiles in baijiu fermentation. Further investigation revealed that environmental microbiota associated with Baijiu fermentation showed a distinct separation between outdoor and indoor settings, especially in the 70-year-old workshop (workshop 70y). The unique distribution of environmental microbes in workshop 70y did not only accelerate microbial succession 5 days earlier, but also significantly enhanced ester production, with an increase from 60.63 μg/mL to 155.31 μg/mL. Source tracking revealed that the rich indoor environmental microbes in the workshop 70y dominated the whole fermentation, while the 2-year-old workshop (workshop 2y) and the 20-year-old workshop (workshop 20y) initially relied on Raw Materials (RM) and Daqu (DQ) microbes, but the control gradually shifted to indoor environment. These findings might offer valuable implications for Baijiu quality control, and enhance our understanding of the functional roles of the environmental microbiome.

New insights into the dominance of mixed fermentation of Staphylococcus cohnii and Staphylococcus saprophyticus in Chinese bacon: Complete genomic and comparative genomic perspectives

Previous studies have demonstrated that Staphylococcus cohnii WX_M8 and S. saprophyticus MY_A10 significantly enhanced the flavor of Chinese bacon in a mixed fermentation. However, due to the complexity of the processing, the contribution of the bacteria is deceptive when investigating only the phenotypic changes at the time of fermentation. In order to clarify the metabolic mechanisms of mixed fermentation, a technological characterization, whole genome and comparative genomics analysis, and metabolites were approached in this study. Results showed that differences in tolerance characteristics existed between WX_M8 and MY_A10. And the genomes of both the two strains consisted of one chromosome and four circular plasmids. Their genome sizes were 2.74 Mp and 2.62 Mp, the GC contents were 32.45% and 33.18%, and the predicted coding genes (CDS) were 2564 and 2541, respectively. Based on the annotation of gene functions and assessment of metabolic pathways in the KEGG database, WX_M8 and MY_A10 strains were found to harbor complete protein degradation and amino acid metabolic pathways, pyruvate and butanol metabolic pathways, and isoleucine metabolic pathways, and their diverse enzyme-encoding genes superimposed the metabolic functions, whereas the alcohol dehydrogenase genes, adh and frmA, achieved complementary functions in the production of esters. Comparative genomics analysis revealed a diversity of encoding genes of aminotransferases and a greater metabolism for sulfur-containing amino acids, aromatic amino acids, and branched-chain amino acids in the mixed fermentation of strains WX_M8 and MY_A10. Metabolites analysis showed that MY_A10 focused on the production of soluble peptides and free amino acids (FAAs), while WX_M8 focused on volatile organic compounds (VOCs), resulting in a significant enhancement of the flavor of Chinese bacon when the two were mixed fermented. This result may provide direction for strains WX_M8 and MY_A10 to be used as starter cultures and targeted to regulate flavor.

Surfactants produced from carbohydrate derivatives: Part 2. A review on the value chain, synthesis, and the potential role of artificial intelligence within the biorefinery concept

AbstractThis comprehensive and critical review explores the synthesis and applications of carbohydrate‐based surfactants within the biorefinery concept, focusing on biobased sugar‐head molecules suitable for use across several manufacturing sectors, including cosmetics, pharmaceuticals, household products, detergents, and foods. The main focus relies on sustainable alternatives to conventional surfactants, which could reduce the final manufacturing carbon footprint of several industrial feedstocks and products. A thorough analysis of raw materials, highlighting the significance of feedstock sources, and the current biobased surfactants and rhamnolipid biosurfactants production trends, is presented. Key organic reactions for the production of sorbitan esters, sucrose esters, alkyl polyglycosides, and fatty acid glucamines, such as glycosidation, acylation, and etherification, as well as the production of rhamnolipids through fermentation are described. Given the scarce literature on the characterization of these surfactant types within the hydrophilic–lipophilic deviation (HLD) framework, the surfactant contribution parameter (SCP) in the HLD equation for sugar‐head surfactants is critically assessed. The economic landscape is also discussed, noting the significant growth in the biobased surfactants and biosurfactant market, driven by environmental awareness and regulatory changes, with projections indicating a substantial market increase in the forthcoming years. Finally, the promising potential of generative artificial intelligence (AI) in developing customized surfactant molecules, with optimized properties for targeted applications, is emphasized as a promising avenue for future research.

Modular Synthesis of Conjugated Aromatic Boronate Esters by Radical Xanthate Addition

AbstractConjugated aromatic boronate esters serve as crucial intermediates in the synthesis of pharmaceuticals and polymer materials. Traditional methods for their synthesis typically involve organoboration of aromatic ring compounds, where pre-constructions of aromatic rings are required. Here, we present a general strategy for the synthesis of diverse conjugated aromatic boronate esters based on the radical addition of xanthates. Through this method, we synthesized various boronate ester xanthates that could be utilized as a platform to furnish conjugated aromatic building blocks, including thiophenes, pyrroles, tetralones, naphthols, and naphthylamines. This cost-effective strategy holds promise as a viable method for the industrial-scale production of (hetero)aromatic boronate esters.

Addition of lactic acid bacteria modulates microbial community and promotes the flavor profiles of Kombucha

This study explores the impact of innovative food processing on food-derived bioactive components through integrating lactic acid bacteria (LAB) in kombucha fermentation. The study showcased how this technique, involving four LAB strains, drastically transformed the beverage's chemical composition, favoring its flavor properties and microbial diversity. LAB integration significantly lessened total and acetic acid content, enhancing kombucha's flavor, especially with the effective strain Lactiplantibacillus plantarum. LAB's presence fostered the production of alcohols and esters further enhancing the kombucha's flavor. Post-72-h quality shifts detected through Principal Component Analysis were potentially attributed to the LAB's role in generating volatile compounds. High-throughput sequencing denoted Zygosaccharomyces, Pichia, Komagataeibacter, and Gluconacetobacter as leading microbial genera, with Pichia correlating strongly with flavor compounds. The study also unveiled six key volatile compounds and their metabolic pathways. Thus, this pilot investigation presents essential insights for future strategies to enhance kombucha flavor, also shedding light on the health-promoting foods sector.

Enhanced upgrading of lignocellulosic substrates by coculture of Saccharomyces cerevisiae and Acinetobacter baylyi ADP1

BackgroundLignocellulosic biomass as feedstock has a huge potential for biochemical production. Still, efficient utilization of hydrolysates derived from lignocellulose is challenged by their complex and heterogeneous composition and the presence of inhibitory compounds, such as furan aldehydes. Using microbial consortia where two specialized microbes complement each other could serve as a potential approach to improve the efficiency of lignocellulosic biomass upgrading.ResultsThis study describes the simultaneous inhibitor detoxification and production of lactic acid and wax esters from a synthetic lignocellulosic hydrolysate by a defined coculture of engineered Saccharomyces cerevisiae and Acinetobacter baylyi ADP1. A. baylyi ADP1 showed efficient bioconversion of furan aldehydes present in the hydrolysate, namely furfural and 5-hydroxymethylfurfural, and did not compete for substrates with S. cerevisiae, highlighting its potential as a coculture partner. Furthermore, the remaining carbon sources and byproducts of S. cerevisiae were directed to wax ester production by A. baylyi ADP1. The lactic acid productivity of S. cerevisiae was improved approximately 1.5-fold (to 0.41 ± 0.08 g/L/h) in the coculture with A. baylyi ADP1, compared to a monoculture of S. cerevisiae.ConclusionThe coculture of yeast and bacterium was shown to improve the consumption of lignocellulosic substrates and the productivity of lactic acid from a synthetic lignocellulosic hydrolysate. The high detoxification capacity and the ability to produce high-value products by A. baylyi ADP1 demonstrates the strain to be a potential candidate for coculture to increase production efficiency and economics of S. cerevisiae fermentations.

Development of a rapid quantitative method of analysis of carbohydrate fatty acid ester reaction mixtures using 1H qNMR

Two new analytical methods, applying absolute 1H qNMR, were developed to monitor product yield and quantify unreacted carbohydrate and fatty acid reactants, in the synthesis of carbohydrate fatty acid esters (CFAE). These methods provide a mass balance of the crude reaction mixtures and diversify the analytical screening and quantitation approaches available within the synthesis of these molecules. Both methods were validated for the model reaction of methyl α-d-glucopyranoside (MAG) and lauric acid (LA) to form the mono ester product, methyl 6-O-dodecanoyl-α-d-glucopyranoside. Analysis in CD3OD by 1H qNMR, with fumaric acid (FA) as an internal standard (IS), allowed monitoring of all reaction components. Alternatively, using CDCl3 and (E)-stilbene as IS enabled the analysis of CFAE and fatty acid. Parameters calculated for method validation included specificity and selectivity, linearity, accuracy, intermediate precision, limit of detection (LOD), limit of quantification (LOQ) and robustness. Both methods provided excellent linearity with R2 > 0.997. The accuracy, precision, and robustness of the method in CD3OD was <2 % uncertainty making it suitable for complete reaction analysis. The method completed in CDCl3 resulted in accuracy, intermediate precision, and robustness of <5 %, except for accuracy in the lowest levels of concentration (>5 %). For all related analytes in the CD3OD and CDCl3 methods, the LOD and LOQ were determined to ensure applicability for the intended use in the assessment of reaction crude composition. Finally, the system suitability was assessed in a scaled lipase catalysed CFAE synthetic reaction. The determined qNMR product yields were verified against isolated purified product yields with <5 % uncertainty.

Catalytic Access to Diastereometrically Pure Four‐ and Five‐Membered Silyl‐Heterocycles Using Transborylation

AbstractSilyl‐heterocycles offer a unique handle to expand and explore chemical space, reactivity, and functionality. The shortage of catalytic methods for the preparation of diverse and functionalized silyl‐heterocycles however limits widespread exploration and exploitation. Herein the borane‐catalyzed intramolecular 1,1‐carboboration of silyl‐alkynes has been developed for the synthesis of 2,3‐dihydrosilolyl and silylcyclobut‐2‐enyl boronic esters. Successful, catalytic carboboration has been achieved on a variety of functionally diverse silyl‐alkynes, using a borane catalyst and transborylation‐enabled turnover. Mechanistic studies, including 13C‐labelling, computational studies, and single‐turnover experiments, suggest a reaction pathway proceeding by 1,2‐hydroboration, 1,1‐carboboration, and transborylation to release the alkenyl boronic ester product and regenerate the borane catalyst.

Catalytic Access to Diastereometrically Pure Four- and Five-Membered Silyl-Heterocycles Using Transborylation.

Silyl-heterocycles offer a unique handle to expand and explore chemical space, reactivity, and functionality. The shortage of catalytic methods for the preparation of diverse and functionalized silyl-heterocycles however limits widespread exploration and exploitation. Herein the borane-catalyzed intramolecular 1,1-carboboration of silyl-alkynes has been developed for the synthesis of 2,3-dihydrosilolyl and silylcyclobut-2-enyl boronic esters. Successful, catalytic carboboration has been achieved on a variety of functionally diverse silyl-alkynes, using a borane catalyst and transborylation-enabled turnover. Mechanistic studies, including 13C-labelling, computational studies, and single-turnover experiments, suggest a reaction pathway proceeding by 1,2-hydroboration, 1,1-carboboration, and transborylation to release the alkenyl boronic ester product and regenerate the borane catalyst.

Esters and higher alcohols regulation to enhance wine fruity aroma based on oxidation-reduction potential

Fruity aroma is a crucial element in reflecting the flavor of wine, believed to be closely linked to esters and higher alcohols associated with the oxidation-reduction potential (ORP) of wine. In this work, the impact of ORP on the production of esters and higher alcohols, and consequently the fruity aroma in Cabernet Sauvignon (CS) and Ecolly wines were investigated. Results revealed that the maximum concentration of medium-chain fatty acid ethyl esters (MCFAEEs) was achieved at −80 mV, which was 48.78% and 25.10% higher than those of the CK groups (ORP without artificial control) in CS and Ecolly wines, respectively. However, the concentrations of acetates and higher alcohols in CS were not significantly different from that in CK, while those in Ecolly were elevated. Additionally, the temperate fruity aroma in CS and citrus aroma in Ecolly wines were enhanced at −80 mV. Partial least-squares regression further indicated that, higher alcohols contributed positively to these enhanced aromas of CS and Ecolly. MCFAEEs have also been suggested to have a positive impact on the fruity and floral aromas for CS and tropical fruity aroma for Ecolly wines. Our work provides an alternative for improving the aroma quality of wine through fermentation process.

Simultaneous geraniol and citronellol transesterification using Pseudomonas fluorescens lipase for the production of fragrance and flavour esters: A kinetic study

This study aims to develop, for the very first time, a kinetic model for the simultaneous transesterification of geraniol and citronellol using Pseudomonas fluorescens lipase to produce their respective esters. This allows us to test the feasibility of the bioprocess and comprehend the enzyme behaviour, fine-tune process efficiency, and predict process performance. Geranyl and citronellyl esters are key ingredients in fragrance and flavour formulations in the food sector, as well as bioactive compounds for pest and insect repellents in the agricultural sector. Unlocking a greener and sustainable production of these terpene esters directly from plant-derived essential oil is crucial to meet the 2050 net zero targets to produce bio-based chemicals. The simultaneous transesterification of geraniol and citronellol in a batch reactor successfully achieved conversions of 66 % for citronellol and 94 % for geraniol within 5 h. Key optimum conditions were 1:8 molar ratio (geraniol:vinyl acetate), an enzyme loading of 10 wt % of geraniol, temperature of 40 °C, and a stirring speed of 250 RPM. The results indicated that simultaneous transesterification followed a ternary complex mechanism with competitive inhibition by alcohol. Initial testing of rose geranium oil under optimised conditions yielded 32 % citronellol and 50 % geraniol conversion after 30 h. Overall, this study shows promise as a green pathway utilising enzyme catalysis to selectively produce esters from diverse terpene mixtures and can be extended to terpene alcohols derived from flower essential oils.

Preparation and characterization of self-aggregating micelles from stearic acid-modified burdock root polysaccharide

In order to obtain amphiphilic polysaccharide self-assembly micelles, the hydrophobic modification by grafting stearic acid (SA) onto the backbone of burdock root polysaccharide (BRP) was carried out and its main physicochemical properties were characterized. The results showed that the optimal esterification conditions were as follows: reaction time of 2 h, reaction temperature of 55 ℃, system pH of 8.0 and the SA addition of 4 mmol, a maximum substitution degree (DS) of the esterification products was obtained as 0.1012. The FTIR analysis verified that the modified polysaccharide successfully introduced the ester carbonyl group. 1H NMR spectra further confirmed that the esterification reaction occurred. The SA-modified BRP micelles were roughly spherical with uniform dispersion and the particle size was in the range of 259–352 nm, which showed a negative correlation with the DS. The solubility of the esterification products also decreased. The smaller critical micelle concentration (CMC) led to easier formation of self-aggregating micelles and stronger solubilization effect. The above results indicated that SA-modified BRP as a novel carrier material possessed potential to deliver hydrophobic active substances.Graphical

PREPARATION AND CHARACTERIZATION OF BENTONITE CLAY CATALYSTS FOR TRANSESTERIFICATION OF WASTE COOKING OIL INTO BIODIESEL

The development of low-cost green catalytic materials is crucial for the conversion of non-edible vegetable oils or waste materials into biodiesel. The research focuses on the preparation and characterization of aluminium pillared clay and NaOH-doped bentonite clay catalysts for biodiesel production from waste cooking oil using XRF, XRD, FTIR and N2 adsorption-desorption techniques. The molecular profile and functional group assessment of the biodiesel were done using GC-MS and FTIR respectively. XRF analysis revealed the presence of oxides in all samples. The amount of SiO2 in all samples was within the range of 35.303–39.199 wt%. Al2O3 increased from 15.560 to 19.11 wt%, while the interlayer cations decreased after pillaring. FTIR revealed the appearance of peaks which are characteristic of bentonite. The pillaring and impregnation of NaOH with bentonite led to a distortion of certain peaks' intensity, as evidenced by FTIR results. The pillaring caused an increase in BET surface area and pore volume compared to bentonite from 302.1 to 366.4 m2/g, and 0.186 to 0.189 cc/g respectively, while a decrease in surface area and pore volume was observed in NaOH/bentonite due to impregnation. The XRD data have shown the increase of basal d-spacing of pillared clay from 12.65 to 16.49 Å relative to bentonite with a decrease to 12.45 in the case of NaOH/bentonite. The catalysts prepared outperformed neat bentonite with NaOH/bentonite, resulting in the highest yield of (83 ± 1.80). GC-MS, FTIR, and physicochemical analyses confirmed the production of fatty acid methyl esters.

Effectiveness of sulfuric acid and hydrochloric acid catalysts in the esterification of frankincense cinnamic acid with ethanol and methanol

This research aims to compare the effectiveness of sulfuric acid and hydrochloric acid catalysts in the esterification of frankincense cinnamic acid (STYRAX paraleoncomud PERK). Esterification of sulfuric acid catalyst is carried out with ethanol and for hydrochloric acid catalyst with methanol. Esterification was carried out by refluxing a mixture of 1:20 cinnamic acid - ethanol and methanol, with 3 mL of each catalyst at a temperature of 60oC for one hour. The results were rinsed with 3 x 50 mL distilled water and dried with anhydrous sodium sulfate. The results were filtered and verified for functional groups using FTIR and composition analysis using GC – MS. The results of FTIR interpretation show a decrease in absorption intensity (-OH) at 3500 cm-1 as a functional group that reacts compared to the ester results as an indication of the ongoing esterification reaction. The resulting ethyl cinnamate has a high conversion of 84.42%. Methyl cinnamate also has a distinctive ester aroma but is clearer and based on GC-MS, the content of methyl cinnamate is relatively low, namely 34.40%, the remaining cinnamic acid is 37.28%, and various side products of 28.32%. Thus, the catalyst that provides better conversion is sulfuric acid, but it requires further purification by examining the appropriate absorbent and bleaching agent. The brown color of the ester product catalyzed by sulfuric acid is thought to occur due to the oxidation of the cinnamic acid double bond by the catalyst.

Highly Selective Electrochemical Baeyer-Villiger Oxidation through Oxygen Atom Transfer from Water.

The Baeyer-Villiger oxidation of ketones is a crucial oxygen atom transfer (OAT) process used for ester production. Traditionally, Baeyer-Villiger oxidation is accomplished by thermally oxidizing the OAT from stoichiometric peroxides, which are often difficult to handle. Electrochemical methods hold promise for breaking the limitation of using water as the oxygen atom source. Nevertheless, existing demonstrations of electrochemical Baeyer-Villiger oxidation face the challenges of low selectivity. We report in this study a strategy to overcome this challenge. By employing a well-known water oxidation catalyst, Fe2O3, we achieved nearly perfect selectivity for the electrochemical Baeyer-Villiger oxidation of cyclohexanone. Mechanistic studies suggest that it is essential to produce surface hydroperoxo intermediates (M-OOH, where M represents a metal center) that promote the nucleophilic attack on ketone substrates. By confining the reactions to the catalyst surfaces, competing reactions (e.g., dehydrogenation, carboxylic acid cation rearrangements, and hydroxylation) are greatly limited, thereby offering high selectivity. The surface-initiated nature of the reaction is confirmed by kinetic studies and spectroelectrochemical characterizations. This discovery adds nucleophilic oxidation to the toolbox of electrochemical organic synthesis.

Comparison of Performance Properties of Muds Formulated With Synthesized C14 and C16 Esters of Lauric Acid

Drilling muds have relied on a range of base fluids, with mineral oil-based formulations dominating the landscape for decades. However, mineral oil-based muds contain a plethora of toxic aromatic compounds which are persistent in the environment. Hence, the objective of the paper was to synthesize and compare the performance properties of drilling muds formulated with C14 and C16 esters of lauric acid using appropriate standard procedures. Benchmarking of the esters with a reference synthetic base fluid indicated that the esters have suitable physicochemical properties for application as synthetic base drilling fluid. Their kinematic viscosities are within the API recommended range, ethyl laurate (EL) has a lower cloud point relative to the reference, and the two base fluids have higher flash point and electrical stabilities relative to the reference. The results obtained from comparing the rheology of muds prepared with ester products and that prepared with the reference fluid indicate that the muds prepared with ethyl, and n-butyl laurate have higher electrical stability than the mud prepared with the reference base fluid. The results also show that the muds prepared with the esters synthesized in this work displayed better rheology profiles than the mud prepared with the reference synthetic base fluid. However, ethyl laurate (EL) formulated mud had better thermal stability than n-butyl laurate (BL) at the temperature range studied. Through the investigation of these ester-based drilling muds, we showcased the potential of these esters to enhance drilling efficiency, minimize environmental impact, and optimize operational performance.

Synthesis of Methyl Ester from Microalgae Chlorella sp. TAD Using the In-Situ Transesterification Method

Synthesis of methyl ester from Chlorella sp. TAD microalgae was carried out using the in-situ transesterification method. This study aims to determine the methyl ester composition of Chlorella sp. TAD microalgae using the in-situ transesterification method. The in-situ transesterification method is a modified method that allows extraction and transesterification into methyl ester products in one process simultaneously. The in-situ transesterification process lasted 8 hours, followed by a distillation process to remove the n-hexane content and an oven for 2 hours to evaporate the remaining water. The results of the analysis using GC-MS to determine the chemical content of the methyl ester compound from Chlorella sp. TAD, showed the methyl ester composition of 7,10-hexadecanoic methyl ester, 8,11,14-docosatrienoic methyl ester, 9-hexadecanoic methyl ester, hexadecanoic methyl ester, heptadecanoic methyl ester, 10-octadecenoic methyl ester, octadecenoic methyl ester, 9,12-octadecadienoic methyl ester, 10-octadecenoic methyl ester, 2-hexyl cyclopropaneoctanoic methyl ester, eicosanoic methyl ester, 10-heptadecen-8-ynoic acid methyl ester, nonahexacontanoic methyl ester, and tetracosanoic methyl ester.

Transcriptomics to evaluate the influence mechanisms of ethanol on the ester production of Wickerhamomyces anomalus with the induction of lactic acid

Wickerhamomyces anomalus is one of the most important ester-producing strains in Chinese baijiu brewing. Ethanol and lactic acid are the main metabolites produced during baijiu brewing, but their synergistic influence on the growth and ester production of W. anomalus is unclear. Therefore, in this paper, based on the contents of ethanol and lactic acid during Te-flavor baijiu brewing, the effects of different ethanol concentrations (3, 6, and 9% (v/v)) combined with 1% lactic acid on the growth and ester production of W. anomalus NCUF307.1 were studied and their influence mechanisms were analyzed by transcriptomics. The results showed that the growth of W. anomalus NCUF307.1 under the induction of lactic acid was inhibited by ethanol. Although self-repair mechanism of W. anomalus NCUF307.1 induced by lactic acid was initiated at all concentrations of ethanol, resulting in significant up-regulation of genes related to the Genetic Information Processing pathway, such as cell cycle-yeast, meiosis-yeast, DNA replication and other pathways. However, the accumulation of reactive oxygen species and the inhibition of pathways associated with carbohydrate and amino acid metabolism may be the main reason for the inhibition of growth in W. anomalus NCUF307.1. In addition, 3% and 6% ethanol combined with 1% lactic acid could promote the ester production of W. anomalus NCUF307.1, which may be related to the up-regulation of EAT1, ADH5 and TGL5 genes, while the inhibition in 9% ethanol may be related to down-regulation of ATF2, EAT1, ADH2, ADH5, and TGL3 genes.

Analysis of Improving the Quality of Fatty Acid Methyl Ester (FAME) Products Against Acid Value (AV) Levels Using the Six Sigma and Kaizen Methods

. PT XYZ is a palm oil derivative processing company that produces biodiesel / FAME (Fatty Acid Methyl Ester) products. However, there are several obstacles that still occur during the company's production process which causes the acid value (AV) level of FAME products to not meet specifications and there are 3% defective products. Therefore, this study aims to determine the improvement plan by applying kaizen to the Six Sigma improvement stage and reducing outspec products in the FAME production process. The results of the research conducted using the six sigma method show that the company has a DPMO value of 71,459 and a sigma value of 2.96 which is in the average position of the industry in Indonesia based on the results of data processing. While recommendations for improvement by implementing kaizen include training machine operators, making standard operating procedures (SOPs) for machine inspections on each shift, reducing the amount of strearin added to AV raw materials before pre-treatment, maintenance and machine calibration. This step are expected to overcome the main problems identified in the study.