Residual Sugar Research Articles

Influence of indigenous non-Saccharomyces yeast strains on the physicochemical and sensory properties of wine fermentation: a promising approach to enhancing wine quality

This study explores the potential of indigenous non-Saccharomyces yeasts isolated from Vitis vinifera L. grape skins to improve the quality of regional wines by enhancing their physicochemical and sensory characteristics. Five promising yeast strains were identified at different stages of fermentation: Hanseniaspora opuntiae (J1Y-T1), H. guilliermondii (Y5P-T5), H. uvarum (JF3-T1N), Pichia kudriavzevii (Y8P-T8), and Starmerella bacillaris (WMP4-T4). Among these, H. uvarum and S. bacillaris were particularly noteworthy due to their superior alcohol production, achieving levels of 8.16 ± 0.05% and 8.04 ± 0.04% (v/v), respectively, and demonstrating higher alcohol tolerance even in later fermentation stages. Hanseniaspora uvarum also showed exceptional resilience, with a half-life of 3.34 ± 0.03 days and a Km value of 1.0200 ± 0.0100 mol L⁻¹, achieving the highest biomass even in the later stages of fermentation. High-Performance Liquid Chromatography analysis revealed that while tartaric acid levels remained constant, malic acid content decreased, and acetic acid was produced by all strains. Solid-Phase Microextraction-Gas Chromatography Mass Spectrometry identified ethyl acetate as the dominant volatile compound, with H. uvarum producing the highest concentration (43.411 ± 1.602%), contributing to a fruitier aroma and flavor. The combined attributes of H. uvarum higher alcohol content, enhanced fruity notes, improved clarity, lower acetic acid (0.52 ± 0.03 g L⁻¹), and significant residual sugar (162.37 ± 2.48 g L⁻¹) make it a promising candidate for improving the overall quality of regional wines. Incorporating H. uvarum into mixed starter cultures with specific Saccharomyces strains could further optimize the wine fermentation process.

Inter-regional characterisation of New Zealand pinot noir wines: Correlation between wine colour, monomeric and polymeric phenolics, tannin composition, antioxidant capacity, and sensory attributes

A total of 116 New Zealand Pinot Noir wines from Central Otago (CO), Marlborough (MLB), and Martinborough (MTB) were analysed for colour, monomeric and total phenolics, antioxidant capacity, and tannins using colourimetric and HPLC methods. Correlations among chemical compositions and analytical techniques were examined. Additionally, a sensory study assessed wine colour and five mouthfeel attributes. Discriminant analyses revealed significant regional characteristics. CO wines displayed unique monomeric anthocyanin profiles and were perceived as softer on the palate. MLB wines showed higher residual sugar but lower colour intensity and tannin concentration. MTB wines exhibited higher colour and robust mouthfeels, linked to higher colour absorbances, polymeric pigments, and tannins. Mouthfeel attributes correlated significantly with wine total phenolics, MCP and HPLC tannin measurements, and the degree of tannin polymerisation (mDP). The combined chemical and sensory data enhanced regional differentiation, demonstrating the importance of integrating comprehensive chemical measurements with sensory evaluations for thorough wine classification.

Enhancing wine fermentation through concurrent utilization of Lachancea thermotolerans and lactic acid bacteria (Oenococcus oeni and Lactiplantibacillus plantarum) or Schizosaccharomyces pombe

Most commercially available red wines undergo alcoholic fermentation by Saccharomyces yeasts, followed by a second fermentation with the lactic acid bacteria Oenococcus oeni once the initial process is complete. However, this traditional approach can encounter complications in specific scenarios. These situations pose risks such as stalled alcoholic fermentation or the growth of undesirable bacteria while the process remains incomplete, leaving residual sugars in the wine. To address these challenges and the issue of low acidity prevalent in warmer viticultural regions, several novel alternatives are available. The alternatives involve the combined use of Lachancea thermotolerans to increase the acidity of the musts, lactic acid bacteria (Oenococcus oeni and Lactiplantibacillus plantarum) to ensure malic acid stability during early alcoholic fermentation stages, and Saccharomyces cerevisiae to properly complete alcoholic fermentation. The study showed variations in the final chemical parameters of wines based on the microorganisms used.

Exploring the potential of wild date palm (Phoenix Sylvestris L. Roxb) fruits for vinegar production in Bangladesh

The wild date palm (Phoenix Sylvestris L. Roxb), indigenous to Bangladesh, remains underutilized for creating consumable products. This study explores the potential of wild date palm fruit as a valuable food ingredient by converting its juice into vinegar through a two-step fermentation process. Juices with varying total soluble solids (TSS) concentrations of 10%, 15%, 20%, and 25% were subjected to sequential alcoholic and acetic acid fermentation, yielding four vinegar samples (S1, S2, S3, and S4, respectively). During anaerobic fermentation with Saccharomyces cerevisiae, results indicated a significant increase in alcohol content and a corresponding decrease in pH (p ≤ 0.05) with rising TSS levels. Subsequent acetic fermentation utilizing Acetobacter species converted the alcohol into acetic acid, with the 25% TSS vinegar demonstrating the highest nutritional value, acidity, residual reducing sugar, alcohol content, and macro minerals (K, Ca, P, Mg, Na) among the samples. Additionally, increased TSS resulted in a significant rise in density and a decrease in electrical conductivity and linear color change (p ≤ 0.05). All vinegar samples exhibited notable total phenolic content and free radical scavenging capacity. This study underscores the potential of wild date palm fruits in producing high-quality vinegar, offering a novel utilization avenue for this indigenous resource.

The Potential of Co-Fermentation with Pichia kluyveri and Saccharomyces cerevisiae for the Production of Low-Alcohol Craft Beer

The potential health impacts of moderate alcohol consumption have long been debated. The COVID-19 pandemic has heightened public awareness of health concerns, creating a clear market opportunity for low-alcohol craft beer development. This study investigated the possibility of low-alcohol craft beer by co-fermentation with different ratios of Pichia kluyveri (P. kluyveri) and Saccharomyces cerevisiae (SC) according to the established quality indexes. Specifically, this study was conducted to identify the low-alcohol craft beer quality by fermentation kinetics, growth kinetics, apparent attenuation (AA), real attenuation (RA), residual sugar content, alcohol by volume (ABV), and volatile organic compounds. This study demonstrated that the co-fermentation of SC and P. kluyveri in a 1:10 ratio produced an ABV of 2.98% (v/v). In addition, high concentrations of isoamyl acetate and phenyl ethyl acetate revealed banana, rose, apple, and honey flavors, respectively. Overall, this study revealed that the fermentation of P. kluyveri and SC by co-fermentation and the fermentation process by adjusting the yeast composition developed a craft beer with low alcohol content and rich aroma while establishing the quality indicators.

Response mechanism of Saccharomyces cerevisiae under benzoic acid stress in ethanol fermentation

Sugarcane molasses is an ideal economical raw material for ethanol production because of its wide availability, low cost and nutrient content. However, benzoic acid compounds with toxic effects on yeast cells are commonly found in sugarcane molasses. At present, the molecular mechanism of the toxic effects of benzoic acid on Saccharomyces cerevisiae has not been elucidated. Here, the toxic effect of exogenous benzoic acid on S. cerevisiae GJ2008 cells was studied, and the genes differentially expressed in S. cerevisiae GJ2008 after 1.2 g/L benzoic acid stress were identified via Illumina RNA-Seq technology. The results indicated that benzoic acid significantly inhibited yeast cell growth, prolonged their rapid growth period, and ultimately reduced their biomass. During ethanol fermentation using 250 g/L sucrose under 1.2 g/L benzoic acid stress, several adverse effects were observed, such as high residual sugar content, low ethanol concentration and low fermentation efficiency. In addition, the cell morphology was damaged, the cell membrane permeability increased, intracellular nucleic acid and protein leakage increased, and the malondialdehyde content significantly increased. Moreover, the cells protected themselves by significantly increasing the intracellular glycerol content. Fourier transform infrared spectroscopy proved that benzoic acid could reduce the degree of unsaturation and increase cell membrane permeability by changing the yeast cell wall and cell membrane composition, leading to cell damage and even death. Transcriptomic analysis revealed that under benzoic acid stress, the expression of genes associated with sucrose and starch metabolism, thiamine metabolism, the glycolysis pathway, fructose and mannose metabolism, galactose metabolism and ABC transporters was significantly downregulated. The expression of genes related to ribosomes, lipid metabolism, ribosome biosynthesis, nucleic acid metabolism, arginine and proline metabolism, RNA polymerase, metabolism related to cofactor synthesis, and biosynthesis of valine, leucine, and isoleucine was significantly upregulated. These results indicated that benzoic acid inhibited glycolysis and reduced sugar absorption and utilization and ATP energy supply in yeast cells. In response to stress, genes related to the ribosome bioanabolic pathway were upregulated to promote protein synthesis. On the other hand, the expression of ELO1, SUR4, FEN1 and ERG1 was upregulated, which led to extension of long-chain fatty acids and accumulation of ergosterol to maintain cell membrane structure. In conclusion, this paper provides important insights into the mechanism underlying the toxicity of benzoic acid to yeast cells and for realizing high-concentration ethanol production by sugarcane molasses fermentation.

Deep learning and feature reconstruction assisted vis-NIR calibration method for on-line monitoring of key growth indicators during kombucha production

Artificial intelligence (AI) technology is advancing the digitization and intelligence development of the food industry. A promising application is using deep learning-assisted visible near-infrared (vis-NIR) spectroscopy to monitor residual sugar and bacterial concentration in real-time, ensuring kombucha quality during production. The feature fingerprints of residual sugar and bacterial concentration were extracted by four variable selection algorithms and then reconstructed using serial and parallel processing methods. Based on these reconstructed features, Partial Least Squares (PLS) and Convolutional Neural Networks (1DCNN and 2DCNN) models were developed and compared. The experimental results showed that the 2DCNN model based on reconstruction features achieved superior performance. The RPDs of the residual sugar and bacterial concentrations models were 4.49 and 6.88, while the MAEs were 0.42 mg/mL and 0.04 (Abs), respectively. These results suggest that the proposed modeling strategy effectively supports quality control during kombucha production and provides a new perspective for spectral analysis.

Studying how dry extract can affect the aroma release and perception in different red wine styles.

Four red wine matrices representing different red wine styles with the same VOCs (volatile organic compounds), were obtained by enriching a bleed wine with increasing amounts of deodorized dry extract obtained from the pressed wine of the same vinification. The release of VOCs was determined by solid phase micro-extraction-gas chromatography-mass spectrometry (SPME-GC-MS), in conditions mimicking those applied during sensory assessments. Results show that even though the perception of the overall odor intensity was not significantly influenced by the matrix, this latter modulated the odor profiles: at rising wine dry extract, fruity, floral odors decreased, while dehydrated fruit, woody-toasty, vegetal-earthy notes increased. These changes cannot be fully explained by the observed significant influence of the matrix on the release of VOCs or by their correlations with the considered matrix components (ethanol, residual sugars, phenolics, pH), but findings suggest that perceptual interactions are involved. This study could be useful in pressing and blending management for wine aroma quality also considering wine compositional trends under the current climate change context. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Metabolic engineering of the substrate utilization pathway in Escherichia coli increases L-lysine production

L-lysine is an essential amino acid with broad applications in the animal feed, human food, and pharmaceutical industries. The fermentation production of L-lysine by Escherichia coli has limitations such as poor substrate utilization efficiency and low saccharide conversion rates. We deleted the global regulatory factor gene mlc and introduced heterologous genes, including the maltose phosphotransferase genes (malAP) from Bacillus subtilis, to enhance the use efficiency of disaccharides and trisaccharides. The engineered strain E. coli XC3 demonstrated improved L-lysine production, yield, and productivity, which reached 160.00 g/L, 63.78%, and 4.44 g/(L‧h), respectively. Furthermore, we overexpressed the glutamate dehydrogenase gene (gdhA) and assimilated nitrate reductase genes (BsnasBC) from B. subtilis, along with nitrite reductase genes (EcnirBD) from E. coli, in strain E. coli XC3. This allowed the construction of E. coli XC4 with a nitrate assimilation pathway. The L-lysine production, yield, and productivity of E. coli XC4 were elevated to 188.00 g/L, 69.44%, and 5.22 g/(L‧h), respectively. After optimization of the residual sugar concentration and carbon to nitrogen ratio, the L-lysine production, yield, and productivity were increased to 204.00 g/L, 72.32%, and 5.67 g/(L‧h), respectively, in a 5 L fermenter. These values represented the increases of 40.69%, 20.03%, and 40.69%, respectively, compared with those of the starting strain XC1. By engineering the substrate utilization pathway, we successfully constructed a high-yield L-lysine producing strain, laying a solid foundation for the industrial production of L-lysine.

Bacterial nanocellulose by static, static intermittent fed-batch and rotary disc bioreactor-based fermentation routes using economical black tea broth medium: A comparative account

Bacterial nanocellulose was produced here using static, static intermittent-fed batch (SIFB) and rotary disc bioreactor (RDB) mode. Economical black tea broth media with symbiotic consortia of bacteria and yeast (SCOBY) was used towards feasible BNC production (instead of commercial NCIM 2526 strain and conventional HS media). The physicochemical characterization of BNC produced in all three modes via FE-SEM, ATR-FTIR, XRD and TGA results showed a highly porous morphology, mostly Iα form, good crystallinity and thermal stability, respectively. BNC crystallinity lies in the range of 68 % (RDB) to 79.4 % (static and SIFB). Water retention value (86 to 93 %) and moisture content (85 to 93 %) are high for BNC produced in all three modes. Commendable difference in the BNC yield, sugar consumption, conversion yield and residual sugar was observed using different methods. Highest BNC yield 29.4 ± 0.66 gL−1 was obtained under SIFB method as compared to static mode (13.6 ± 0.32 g L−1). Under RDB, a negligible amount of BNC i.e., 1.0 ± 0.2 g L−1 was produced. SCOBY with BTB medium was found unsuitable for BNC production under RDB and needs further investigation. Thus, this comparative study offers a way to produce a commendable amount of low-priced BNC for various techno-industrial usage.

Impact of must clarification treatments on chemical and sensory profiles of kiwifruit wine

This study examined the effect of various clarification treatments on the physicochemical properties, volatile compounds, and sensory attributes of kiwi wines produced from five different kiwifruit (Actinidia deliciosa) varieties. The degree of clarification had a minimal impact on physicochemical parameters, including the content of residual sugar, ethanol, volatile acid, titratable acidity (except for the kiwifruit variety ‘Qinmei’), and the pH value. However, wines made from unclarified juices (muddy juice and pulp) displayed a higher glycerol content than those made from clarified juices. The cluster heat map and principal component analyses (PCA) demonstrated that kiwi wines produced from clarified kiwi juices possessed a higher ester content, whereas muddy juice and pulp wines contained elevated levels of higher alcohols. Quantitative descriptive analysis (QDA) indicated that clarified juice wines outperformed muddy juice and pulp wines in terms of purity, typicality, harmony, intensity, and freshness, with negligible differences in terms of palate acidity. Moreover, the clarified juice wines featured more characteristic kiwi wine aromas (kiwifruit, passionfruit, and pineapple) compared with that of the muddy juice and pulp wines, which exhibited an increased grassy flavour. Although the 100-NTU kiwifruit juice-fermented wine did not show an advantage in the cluster heat map and PCA, it presented better freshness, typicality, and intensity in the QDA, as well as a more passionfruit aroma. Based on the orthogonal partial least-squares discriminant analysis, A. deliciosa ‘Xuxiang’ was deemed to be the most suitable variety for vinification. This study provides crucial insights for enhancing the production of high-quality kiwi wine.

Kinetic Evaluation of the Production of Mead from a Non-Saccharomyces Strain.

There is a growing market for craft beverages with unique flavors. This study aimed to obtain a palate-pleasing mead derived from Pichia kudriavzevii 4A as a monoculture. Different culture media were evaluated to compare the fermentation kinetics and final products. The crucial factors in the medium were ~200 mg L-1 of yeast assimilable nitrogen and a pH of 3.5-5.0. A panel of judges favored the mead derived from Pichia kudriavzevii 4A (fermented in a medium with honey initially at 23 °Bx) over a commercial sample produced from Saccharomyces cerevisiae, considering its appearance, fruity and floral flavors (provided by esters, aldehydes, and higher alcohols), and balance between sweetness (given by the 82.91 g L-1 of residual sugars) and alcohol. The present mead had an 8.57% v/v ethanol concentration, was elaborated in 28 days, and reached a maximum biomass growth (2.40 g L-1) on the same fermentation day (6) that the minimum level of pH was reached. The biomass growth yield peaked at 24 and 48 h (~0.049 g g-1), while the ethanol yield peaked at 24 h (1.525 ± 0.332 g g-1), in both cases declining thereafter. The Gompertz model adequately describes the kinetics of sugar consumption and the generation of yeast biomass and ethanol. Pathogenic microorganisms, methanol, lead, and arsenic were absent in the mead. Thus, Pichia kudriavzevii 4A produced a safe and quality mead with probable consumer acceptance.

Vinasse treated with charcoal as a molasses diluent for ethanol fermentation.

The demand for new products derived from agro-industrial residues has increased recently. Furthermore, vinasse, a wastewater from ethanol production, needs treatment to be reused in the sugarcane industry, reducing industrial water consumption. This study performed vinasse filtration with charcoal from industrial sugarcane residues and used filtered molasses dilution in ethanolic fermentation. There were five treatments in randomized blocks with three repetitions. The treatments included deionized water and natural vinasse as positive and negative controls, respectively, and filtered vinasse from charcoal made from bamboo, sugarcane bagasse, and straw. Hence, fermentation for ethanol production was performed. Compared with natural vinasse, filtered vinasse with all types of charcoal showed lower soluble solids, total residual reducing sugars, higher ethanol concentrations, and greater fermentative efficiency. Filtered vinasse from bagasse and straw charcoals had efficiencies of 81.14% and 77.98%, respectively, in terms of ethanol production, which are close to those of deionized water (81.49%). In a hypothetical industry, vinasse charcoal filtration and charcoal regeneration should prevent 84.12% of water consumption from environmental resources. This process is feasible because it uses a product of sugarcane residue to treat wastewater and reduce industrial water consumption and vinasse disposal.

Assessment of Wine Quality, Traceability and Detection of Grapes Wine, Detection of Harmful Substances in Alcohol and Liquor Composition Analysis

Abstract: Wine production is the result of the interaction between various strains and grapes, and its good quality is also affected by many factors. Aureobasidium, Cladosporium, Candida, Filobasidium, Hanseniaspora, Hannaella, Saccharomyces, Wickerhamomyce, Alternaria, Starmerella, Acetobacter, Papiliotrema, Bradyrhizobium, Leuconostoclia, Gluconobacter, Comamonas, and Massilia, are significantly correlated with changes of physiological properties and volatile compounds. Phenolic compounds, shortened as phenolics, are a vital parameter to the quality of wine, and wine phenolics include two main families: non-flavonoids, which consist of hydroxybenzoic acids (HBAs), hydroxycinnamic acids (HCAs), and stilbenes, and flavonoids, comprising flavonols, flavan-3-ols, and anthocyanins. Wine quality is determined by either sensory tests or physicochemical tests, and the latter analyse the wine’s chemical parameters such as sugar, pH, and alcohol level. The most important constituents found in wine are Terpenes; Aldehydes, Pyrazines, Esters, Ketones and diketones, Mercaptans, and Lactones. In wine quality analysis, the most chief variables are volatile acidity, alcohol, sulphates, citric acid, density, total sulfur dioxide, chlorides, pH, fixed acidity, free sulfur dioxide, and residual sugar. Some classifiers utilized for wine quality prediction in machine learning are: k-Nearest Neighbor (KNN), Random Forest, Decision Tree, Support Vector Machines, Linear Regression, Stochastic Gradient Descent, Artificial Neural Networks (ANN), and Naive Bayes. This article is aimed to review wine quality parameters, detection and traceability of wine, and detection of harmful substances in alcohol and liquor composition analysis.

Pre-adaptation of yeast (Saccharomyces cerevisiae) strains to very high gravity can improve fermentation parameters and reduce osmotic stress

AbstractThis study investigated improvements in sugarcane ethanol production by adapting yeast strains for very high gravity fermentation. Two yeast strains (C22 and Y904) were adapted in eight fermentation cycles with increasing initial sugar content from 56.2 to 296.1 g L−1(Experiment 1). After the last cycle, the “adapted” yeasts were recycled in a wort containing 296.1 g L−1initial sugar and compared with their respective strains that were not subjected to the adaptation process (Experiment 2). Fermentative parameters were analyzed and the osmotic stress on yeast cell morphology was assessed by scanning electron microscopy (SEM). In Experiment 1, along the fermentation cycles, strain Y904 showed a decrease in cell viability after sugar concentration of 223 g L−1. SEM images showed that Y904 cells were wrinkled after this cycle. In the case of strain C22, no differences in cell viability were observed along the cycles. However, for both strains, the residual sugars were relatively high and the ethanol content was below the maximum potential. In Experiment 2, for strain Y904, no differences were observed between adapted and non-adapted yeasts in terms of ethanol content, cell viability, and morphology. In the case of strain C22, cell viability and final ethanol content were significantly higher in the adapted yeast, which had cells less damaged by the osmotic stress. In conclusion, the study supports the importance of yeast strain selection and adaptation for efficient VHG fermentation, by demonstrating the superior performance of yeast strain C22 in response to increasing initial sugar content.

Isolation and identification of non‐Saccharomyces yeasts and their flavour characteristics while brewing Yinhong plum wine

AbstractThe objective of this study was to screen non‐Saccharomyces yeast suitable for enhancing the aroma of Yinhong plum wine. Five non‐Saccharomyces yeasts with strong ester‐producing ability, namely, Wa3 (Wickerhamomyces anomalus), Hu12 (Hanseniaspora uvarum), Pk2A2, PkW2 and PkY2 (Pichia kluyveri), were selected from various naturally fermented fruit juices for molecular biological identification, analyses of physiological characteristics and tolerance and determination of their effects on the flavour of Yinhong plum wine. Analysis of brewing characteristics showed that they differed in their abilities of producing acetic acid, hydrogen sulfide, killer activity and tolerance. Among them, Wa3 showed the best tolerance to high concentrations of alcohol, sugar and SO2. Compared to the control Saccharomyces cerevisiae FX10, Yinhong plum wine fermented with non‐Saccharomyces yeast exhibited a decrease in alcohol content, while residual sugar, glycerol content and the types and quantities of volatile compounds all showed an increase. Among the fermented wines, PkY2 generated the highest content of ester compounds in the fermented wine, which was 5.66 times higher than that generated by the control. The compounds produced by PkY2 were closely related to various ethyl and acetate odour‐active compounds (odour‐active value >1), which could impart a rich floral and fruity aroma to Yinhong plum wine. Sensory analysis revealed that both floral and fruity aromas were significantly increased in Yinhong plum wine fermented by non‐Saccharomyces yeasts, with the highest scores of floral and fruity aromas for PkY2. In conclusion, a Pichia kluyveri strain, PkY2, with excellent brewing characteristics and potential for enhancing the aroma of Yinhong plum wine was identified.

Optimization of the fermentative production of L-methionine by engineered Escherichia coli

As the only essential amino acid containing elemental sulphur, L-methionine has important physiological and biochemical functions in living organisms. However, the fermentative production of L-methionine has not met the requirements of industrial production because of its low production level. In this paper, the fermentation process of an efficient L-methionine producing strain E. coli W3110ΔIJAHFEBC trc-fliY trc-malY/PAM glyA-22 metF constructed previously was systematically optimized. Based on the optimal initial glucose concentration, the effects of different fed-batch fermentation processes, including DO-Stat, pH-Stat, controlling residual sugar control at different level and feeding glucose with constant rate, on L-methionine fermentation were studied. It was found that the control of glucose concentration greatly affected the fermentation process. Subsequently, an optimal fed-batch fermentation process was developed, where the L-methionine titer was increased to 31.71 g/L, the highest yield reported to date, while the fermentation time was shortened to 68 h. Meanwhile, a fermentation kinetics model under the optimal fed-batch fermentation conditions was established, which fitted well with the biosynthesis process of L-methionine. This study may facilitate further development of the fermentative production of L-methionine.

Microbial fermentation-based synthesis of nano-curcumin suggesting the role of pullulan in nano-formulation

Curcumin is a multitargeting nutraceutical with numerous health benefits, however, its efficacy is limited due to poor aqueous solubility and reduced bioavailability. While nano-formulation has emerged as an alternative to encounter such issues, it often involves use of toxic solvents. Microbial synthesis may be an innovative solution to address this lacuna. Present study, for the first time, reports exploitation of Aureobasidium pullulans RBF4A3 for production of nano-curcumin. For this purpose, Aureobasidium pullulans RBF4A3 was inoculated in YPD media along with curcumin (0.1 mg/mL) and incubated for 24 h, 48 h, and 72 h. Subsequently, residual sugar, biomass, EPS concentration, curcumin concentration, and curcumin nanoparticle size were measured. As a result, nano-curcumin with an average particle size of 31.63 nm and enhanced aqueous solubility was obtained after 72 h. Further, investigations suggested that pullulan, a reducing polysaccharide, played a significant role in curcumin nano-formulation. Pullulan-mediated nano-curcumin formulation, with an average particle size of 24 nm was achieved with conversion rate of around 59.19 %, suggesting improved aqueous solubility. Additionally, the anti-oxidant assay of the resulting nano-curcumin was around 53.7 % per μg. Moreover, kinetics and thermodynamic studies of pullulan-based nano-curcumin revealed that it followed first-order kinetics and was favored by elevated temperature for efficient bio-conversion. Also, various physico-chemical investigations like FT-IR, NMR, and XRD reveal that pullulan backbone remains intact while forming curcumin nanoparticle. This study may open up new avenues for synthesizing nano-polyphenols through a completely green and solvent free process with plausible diverse applications.

The Use of Molasses in Producing Bioethanol Catalyzed by Candida tropicalis (Isolated from Cocos nucifera. L) Immobilized MnFe2O4 Coated-Chitosan

Bioethanol is a sustainable fuel product to be an alternative energy source. Therefore, the study aims to observe and analyze the effect of MnFe2O4 coated-chitosan in increasing bioethanol production. This bioethanol was produced from molasses with a high total sugar content of up to 50% with Candida tropicalis as the microorganism. Fermentation is divided into two parts, namely using free C. tropicalis and C. tropicalis immobilized MnFe2O4 coated-chitosan. There was electrostatic interaction between MnFe2O4 and chitosan in 578 cm-1 and 659 cm-1 of FTIR, cubic spinel pattern in XRD, and SEM surface image of C. tropicalis immobilized MnFe2O4 coated-chitosan interaction. These characterization results show very good properties as a biocatalyst. The highest concentration was produced by fermentation using C. tropicalis immobilized MnFe2O4 coated-chitosan about 4.35% with residual sugar of 8.46 g/L. In summary C. tropicalis immobilized MnFe2O4 coated-chitosan have the potential to improve bioethanol products.
 Keywords: Candida tropicalis, fermentation, MnFe2O4 coated-chitosan, molasses

An integrated approach to explore the microbial biodiversity of natural milk cultures for cheesemaking

The use of natural milk culture (NMC) represents a key factor in PDO Montasio cheeses, contributing to its distinctive sensory profile. The complex microbial ecosystem of NMCs is the result of heat treatment and incubation conditions, which can vary considerably among different production plants. In this study, the microbiota of NMCs collected from 10 PDO Montasio cheese dairies was investigated employing colony counts and metagenomic analysis. Furthermore, residual sugars, organic acids, and volatile profiles were quantitatively investigated. Results showed that Streptococcus thermophilus was the dominant species in all NMCs, and a subdominant population made of other streptococci and L. salivarius was also present. The incubation temperature appeared to be the main driver of biodiversity in NMCs. Metagenomics allowed us to evidence the presence of minor species involving safety (e.g., Staph. aureus) as well as possible functional aspects (Next Generation Probiotics). Statistical analysis based on residual sugars, organic acids, and volatiles' content allowed to correlate the presence of specific microbial groups with metabolites of great technological and sensory relevance, which can contribute to giving value to the artisanal production procedures of NMCs and clarify their role in the creation of the characteristics of PDO Montasio cheese.