Unlocking the potential of sugarcane leaf waste for sustainable methane production: Insights from microbial pre-hydrolysis and reactor optimization.

Sugarcane leaf waste, a byproduct of the growing global sugar industry, challenges agricultural waste management. This study explores its potential for methane production via anaerobic digestion. A microbial pre-hydrolysis, using lignocellulose-degrading bacteria, enhanced soluble chemical oxygen demand at an optimal initial substrate concentration of 40 g-volatile solid/L. Comparative analysis with untreated and bioaugmented leaves revealed the pre-hydrolyzed leaves achieved the highest methane production rate (MPR) at 14.0 ± 0.5 mL-CH4/L·d, surpassing others by 1.47 and 1.67 times. Two continuous stirred tank reactors were employed to assess the optimal hydraulic retention time (HRT). Results showed a stable methane production with an HRT of 25 days, yielding high MPRs: 88.70 ± 0.63 mL-CH4/L·d from pre-hydrolyzed sugarcane leaves and 82.57 ± 1.22 mL-CH4/L·d from microbial consortium-augmented leaves. A 25-day HRT fosters high microbial diversity with Bacteroidota, Firmicutes, Chloroflexi, and Verrucomicrobiota dominance, indicating favorable conditions. Conversely, a 20-day HRT results in lower diversity due to unfavorable factors like low pH during organic overloading, leading to increased concentrations of volatile fatty acids and lactic acid, with Firmicutes as the predominant phylum. This study highlights sugarcane leaf waste's potential as a valuable resource for sustainable methane production.

Conversion of carbon dioxide in biogas into acetic acid by Clostridium thailandense immobilized on porous support materials.

This study aimed to convert CO2 in biogas into acetic acid using immobilized Clostridium thailandense cells on various support materials, including activated carbon, expanded clay, and coir. Immobilized cells and free cells were evaluated for their CO2 conversion ability into acetic acid using H2 as an electron donor at an H2 to CO2 in biogas ratio of 2:1 (v/v), 30 °C, 150 rpm. Results showed that immobilized cells on activated carbon increased CH4 content to 96.9% (v/v), and acetic acid production to 15.65 mmol/L within 96 h. These values outperformed free cells. The activated carbon-immobilized cells could be reused two times without losing efficacy in the purification of biogas and acetic acid production. This work indicates that using the immobilized cells offers a sustainable approach to biogas upgrading, reducing the environmental footprint of biogas production by increasing its energy content and purity.

Two-Stage and One-Stage Anaerobic Co-digestion of Vinasse and Spent Brewer Yeast Cells for Biohydrogen and Methane Production.

This study aimed to evaluate the two-stage and one-stage anaerobic co-digestion of vinasse and spent brewer yeast cells (SBY) for biohydrogen and methane production. Optimization of the vinasse-to-SBY ratio and fly ash concentration of the two-stage and one-stage production processes was investigated. In the two-stage process, the vinasse-to-SBY ratio and fly ash concentration were optimized, and the leftover effluent was used for methane production. The optimum conditions for biohydrogen production were a vinasse-to-SBY ratio of 7:3% v/w and fly ash concentration of 0.4% w/v, in which the maximum hydrogen yield was 43.7 ml-H2/g-VSadded. In contrast, a vinasse-to-SBY ratio of 10:0% v/w and fly ash concentration of 0.2% w/v were considered optimal for methane production, and resulted in a maximum methane yield of 214.6 ml-CH4/g-VSadded. For the one-stage process, a vinasse-to-SBY ratio of 10:0% v/w and fly ash concentration of 0.1% w/v were considered optimal, and resulted in a maximum methane yield of 243.6 ml-CH4/g-VSadded. In the two-stage process, the energy yield from hydrogen (0.05-0.47 kJ/g-VSadded) was 0.62%-11.78%, and the major fraction was approximately 88.22%-99.38% gain from methane (3.19-7.73 kJ/g-VSadded). For the one-stage process, the total energy yield distribution ranged from 4.20 to 8.77 kJ/g-VSadded.

Valorization of spent coffee grounds through integrated bioprocess of fermentable sugars, volatile fatty acids, yeast-based single-cell protein and biofuels production.

Recovering nutrients from waste for biological processes aligns with sustainability principles. This study aimed to convert spent coffee grounds (SCG) into valuable products, including fermentable sugars, volatile fatty acids (VFAs), yeast-based single-cell protein and biofuels. Alkaline pretreatment was conducted before enzymatic hydrolysis, in which the pretreated SCG was hydrolyzed with varying enzyme loadings (20-60 filter paper units (FPU)/g-solid) and solid loadings (3-15 % w/v). The hydrolyzed slurry was utilized for VFAs and hydrogen production, yielding high values of 0.66 g/g-volatile solids (VS) and 109 mL/g-VS, respectively, using an enzyme loading of 50 FPU/g-solid and a solid loading of 3 % (w/v). The derived VFAs were used to cultivate a newly isolated yeast, Candida maltosa KKU-ARY2, resulting in an accumulated protein content of 43.7 % and a biomass concentration of 4.6 g/L. This study highlights the conversion of SCG into essential components, emphasizing the benefits of waste utilization through cascade bioprocesses.

Impact of light spectra on photo-fermentative biohydrogen production by Rhodobacter sphaeroides KKU-PS1.

Purple non-sulphur bacteria can only capture up to 10 % light spectra and only 1-5 % of light is converted efficiently for biohydrogen production. To enhance light capture and conversion efficiencies, it is necessary to understand the impact of various light spectra on light harvesting pigments. During photo-fermentation, Rhodobacter sphaeroides KKU-PS1 cultivated at 30 °C and 150 rpm under different light spectra has been investigated. Results revealed that red light is more beneficial for biomass accumulation, whereas green light showed the greatest impact on photo-fermentative biohydrogen production. Light conversion efficiency by green light is 2-folds of that under control white light, hence photo-hydrogen productivity is ranked as green > red > orange > violet > blue > yellow. These experimental data demonstrated that green and red lights are essential for photo-hydrogen and biomass productions of R. sphaeroides and a clearer understanding that possibly pave the way for further photosynthetic enhancement research.

Evaluation of commercial moving bed media and sugarcane bagasse as packing material in biotrickling filter for hydrogen sulfide removal.

This study compared two biotrickling filter packing materials for hydrogen sulfide removal. Inlet H2S concentrations and empty-bed retention time were tested on the two biotrickling filters. First reactor (BT1) had immobilized sulfur-oxidizing bacteria on commercial moving-bed media, whereas second reactor (BT2) had sulfur-oxidizing bacteria on sugarcane bagasse. The study found that BT1 performed best at 120 s empty-bed retention time, 422.39 g/m3·h hydrogen sulfide loading rate, resulted in 416 g/m3·h hydrogen sulfide elimination capacity. In contrast, BT2 performed best at 180 s empty-bed retention time, 278.77 g/m3·h hydrogen sulfide loading rate, and 273 g/m3·h elimination capacity was achieved. High-throughput sequencing showed Acidithobacillus spp. dominated the sulfur-oxidizing bacteria consortium. Sugarcane bagasse may receive less hydrogen sulfide loading than moving bed medium under optimal conditions, but its low cost and reasonable removal capacity of hydrogen sulfide -containing industrial gases in a biotrickling filter system make it an excellent alternative packing material.

Two-stage biohydrogen and methane production from sugarcane-based sugar and ethanol industrial wastes: A comprehensive review.

The transition to renewable energy sources is crucial to ensure a sustainable future. Although the sugar and ethanol industries benefit from this transition, there are untapped opportunities to utilize the waste generated from the sugar and ethanol process chains through two-stage anaerobic digestion (TSAD). This review comprehensively discusses the utilization of various sugarcane-based industrial wastes by TSAD for sequential biohydrogen and methane production. Factors influencing TSAD process performance, including pH, temperature, hydraulic retention time, volatile fatty acids and alkalinity, nutrient imbalance, microbial population, and inhibitors, were discussed in detail. The potential of TSAD to reduce emissions of greenhouse gases is demonstrated. Recent findings, implications, and promising future research related to TSAD, including the integration of meta-omics approaches, gene manipulation and bioaugmentation, and application of artificial intelligence, are highlighted. The review can serve as important literature for the implementation, improvement, and advancements in TSAD research.

Efficient production of lactic acid from cellulose and xylan in sugarcane bagasse by newly isolated Lactiplantibacillus plantarum and Levilactobacillus brevis through simultaneous saccharification and co-fermentation process.

Sugarcane bagasse is one of the promising lignocellulosic feedstocks for bio-based chemicals production. However, to date, most research focuses mainly on the cellulose conversion process, while hemicellulose remains largely underutilized. The conversion of glucose and xylose derived from lignocellulosic biomass can be a promising strategy to improve utilization efficiencies of resources, energy, and water, and at the same time reduce wastes generated from the process. Here, attempts were made to convert cellulose and xylan in sugarcane bagasse (SB) into lactic acid (LA) through a pre-hydrolysis and simultaneous saccharification and co-fermentation (SScF) process using newly isolated Lactiplantibacillus plantarum TSKKU P-8 and Levilactobacillus brevis CHKKU N-6. The process yielded 91.9 g/L of LA, with a volumetric productivity of 0.85 g/(L·h). This was equivalent to 137.8 ± 3.4 g-LA, a yield on substrate (pretreated SB) of 0.86 g/g, and a productivity of 1.28 g/h, based on a final volume of 1.5 L. On the other hand, pre-hydrolysis and simultaneous saccharification and fermentation (SSF) process using La. plantarum TSKKU P-8 as a monoculture gave 86.7 ± 0.2 g/L of LA and a volumetric productivity of 0.8 g/(L·h), which were equivalent to 104.8 ± 0.3 g-LA, a yield on substrate of 0.65 g/g, and a productivity of 0.97 g/h, based on a final volume of 1.2 L. Mass balance calculated based on mass of raw SB entering the process showed that the SScF process improved the product yield by 32% as compared with SSF process, resulting in 14% improvement in medium-based economic yield.

Microalga Coelastrella sp. Cultivation on Unhydrolyzed Molasses-Based Medium towards the Optimization of Conditions for Growth and Biomass Production under Mixotrophic Cultivation.

Improving biomass production with the utilization of low-cost substrate is a crucial approach to overcome the hindrance of high cost in developing large-scale microalgae production. The microalga Coelastrella sp. KKU-P1 was mixotrophically cultivated using unhydrolyzed molasses as a carbon source, with the key environmental conditions being varied in order to maximize biomass production. The batch cultivation in flasks achieved the highest biomass production of 3.81 g/L, under an initial pH 5.0, a substrate to inoculum ratio of 100:3, an initial total sugar concentration of 10 g/L, and a sodium nitrate concentration of 1.5 g/L with continuous light illumination at 23.7 W/m2. The photobioreactor cultivation results indicated that CO2 supplementation did not improve biomass production. An ambient concentration of CO2 was sufficient to promote the mixotrophic growth of the microalga as indicated by the highest biomass production of 4.28 g/L with 33.91% protein, 46.71% carbohydrate, and 15.10% lipid. The results of the biochemical composition analysis suggest that the microalgal biomass obtained is promising as a source of essential amino acids and pigments as well as saturated and monounsaturated fatty acids. This research highlights the potential for bioresource production via microalgal mixotrophic cultivation using untreated molasses as a low-cost raw material.

Taxonomic and enzymatic basis of the cellulolytic microbial consortium KKU-MC1 and its application in enhancing biomethane production.

Lignocellulosic biomass is a promising substrate for biogas production. However, its recalcitrant structure limits conversion efficiency. This study aims to design a microbial consortium (MC) capable of producing the cellulolytic enzyme and exploring the taxonomic and genetic aspects of lignocellulose degradation. A diverse range of lignocellulolytic bacteria and degrading enzymes from various habitats were enriched for a known KKU-MC1. The KKU-MC1 was found to be abundant in Bacteroidetes (51%), Proteobacteria (29%), Firmicutes (10%), and other phyla (8% unknown, 0.4% unclassified, 0.6% archaea, and the remaining 1% other bacteria with low predominance). Carbohydrate-active enzyme (CAZyme) annotation revealed that the genera Bacteroides, Ruminiclostridium, Enterococcus, and Parabacteroides encoded a diverse set of cellulose and hemicellulose degradation enzymes. Furthermore, the gene families associated with lignin deconstruction were more abundant in the Pseudomonas genera. Subsequently, the effects of MC on methane production from various biomasses were studied in two ways: bioaugmentation and pre-hydrolysis. Methane yield (MY) of pre-hydrolysis cassava bagasse (CB), Napier grass (NG), and sugarcane bagasse (SB) with KKU-MC1 for 5 days improved by 38-56% compared to non-prehydrolysis substrates, while MY of prehydrolysed filter cake (FC) for 15 days improved by 56% compared to raw FC. The MY of CB, NG, and SB (at 4% initial volatile solid concentration (IVC)) with KKU-MC1 augmentation improved by 29-42% compared to the non-augmentation treatment. FC (1% IVC) had 17% higher MY than the non-augmentation treatment. These findings demonstrated that KKU-MC1 released the cellulolytic enzyme capable of decomposing various lignocellulosic biomasses, resulting in increased biogas production.

Valorization of rice straw, sugarcane bagasse and sweet sorghum bagasse for the production of bioethanol and phenylacetylcarbinol.

Open burning of agricultural residues causes numerous complications including particulate matter pollution in the air, soil degradation, global warming and many more. Since they possess bio-conversion potential, agro-industrial residues including sugarcane bagasse (SCB), rice straw (RS), corncob (CC) and sweet sorghum bagasse (SSB) were chosen for the study. Yeast strains, Candida tropicalis, C. shehatae, Saccharomyces cerevisiae, and Kluyveromyces marxianus var. marxianus were compared for their production potential of bioethanol and phenylacetylcarbinol (PAC), an intermediate in the manufacture of crucial pharmaceuticals, namely, ephedrine, and pseudoephedrine. Among the substrates and yeasts evaluated, RS cultivated with C. tropicalis produced significantly (p ≤ 0.05) higher ethanol concentration at 15.3 g L-1 after 24 h cultivation. The product per substrate yield (Yeth/s) was 0.38 g g-1 with the volumetric productivity (Qp) of 0.64 g L-1 h-1 and fermentation efficiency of 73.6% based on a theoretical yield of 0.51 g ethanol/g glucose. C. tropicalis grown in RS medium produced 0.303 U mL-1 pyruvate decarboxylase (PDC), a key enzyme that catalyzes the production of PAC, with a specific activity of 0.400 U mg-1 protein after 24 h cultivation. This present study also compared the whole cells biomass of C. tropicalis with its partially purified PDC preparation for PAC biotransformation. The whole cells C. tropicalis PDC at 1.29 U mL-1 produced an overall concentration of 62.3 mM PAC, which was 68.4% higher when compared to partially purified enzyme preparation. The results suggest that the valorization of lignocellulosic residues into bioethanol and PAC will not only aid in mitigating the environmental challenge posed by their surroundings but also has the potential to improve the bioeconomy.

Advances and perspectives on mass transfer and enzymatic hydrolysis in the enzyme-mediated lignocellulosic biorefinery: A review.

Enzymatic hydrolysis is a critical process for the cellulase-mediated lignocellulosic biorefinery to produce sugar syrups that can be converted into a whole range of biofuels and biochemicals. Such a process operating at high-solid loadings (i.e., scarcely any free water or roughly ≥ 15% solids, w/w) is considered more economically feasible, as it can generate a high sugar concentration at low operation and capital costs. However, this approach remains restricted and incurs "high-solid effects", ultimately causing the lower hydrolysis yields with increasing solid loadings. The lack of available water leads to a highly viscous system with impaired mixing that exhibits strong transfer resistance and reaction limitation imposed on enzyme action. Evidently, high-solid enzymatic hydrolysis involves multi-scale mass transfer and multi-phase enzyme reaction, and thus requires a synergistic perspective of transfer and biotransformation to assess the interactions among water, biomass components, and cellulase enzymes. Porous particle characteristics of biomass and its interface properties determine the water form and distribution state surrounding the particles, which are summarized in this review aiming to identify the water-driven multi-scale/multi-phase bioprocesses. Further aided by the cognition of rheological behavior of biomass slurry, solute transfer theories, and enzyme kinetics, the coupling effects of flow-transfer-reaction are revealed under high-solid conditions. Based on the above basic features, this review lucidly explains the causes of high-solid hydrolysis hindrances, highlights the mismatched issues between transfer and reaction, and more importantly, presents the advanced strategies for transfer and reaction enhancements from the viewpoint of process optimization, reactor design, as well as enzyme/auxiliary additive customization.

Sparking Nano-Metals on a Surface of Polyethylene Terephthalate and Its Application: Anti-Coronavirus and Anti-Fogging Properties.

The nano-metal-treated PET films with anti-virus and anti-fogging ability were developed using sparking nano-metal particles of Ag, Zn, and Ti wires on polyethylene terephthalate (PET) films. Ag nanoparticles were detected on the PET surface, while a continuous aggregate morphology was observed with Zn and Ti sparking. The color of the Ag-PET films changed to brown with increasing repeat sparking times, but not with the Zn-PET and Ti-PET films. The water contact angle of the nano-metal-treated PET films decreased with increasing repeat sparking times. The RT-PCR anti-virus test confirmed the high anti-virus efficiency of the nano-metal-treated PET films due to the fine particle distribution, high polarity, and binding of the nano-metal ions to the coronavirus, which was destroyed by heat after UV irradiation. A highly transparent, anti-fogging, and anti-virus face shield was prepared using the Zn-PET film. Sparking was an effective technique to prepare the alternative anti-virus and anti-fogging films for medical biomaterial applications because of their low cost, convenience, and fast processing.

High Cell Density Cultivation of Paracoccus sp. on Sugarcane Juice for Poly(3-hydroxybutyrate) Production.

High cell density cultivation is a promising approach to reduce capital and operating costs of poly (3-hydroxybutyrate) (PHB) production. To achieve high cell concentration, it is necessary that the cultivation conditions are adjusted and controlled to support the best growth of the PHB producer. In the present study, carbon to nitrogen (C/N) ratio of a sugarcane juice (SJ)-based medium, initial sugar concentration, and dissolved oxygen (DO) set point, were optimized for batch cultivation of Paracoccus sp. KKU01. A maximum biomass concentration of 55.5 g/L was attained using the C/N ratio of 10, initial sugar concentration of 100 g/L, and 20% DO set point. Fed-batch cultivation conducted under these optimum conditions, with two feedings of SJ-based medium, gave the final cell concentration of 87.9 g/L, with a PHB content, concentration, and yield of 36.2%, 32.1 g/L, and 0.13 g/g-sugar, respectively. A medium-based economic analysis showed that the economic yield of PHB on nutrients was 0.14. These results reveal the possibility of using SJ for high cell density cultivation of Paracoccus sp. KKU01 for PHB production. However, further optimization of the process is necessary to make it more efficient and cost-effective.

Clostridium thailandense sp. nov., a novel CO2-reducing acetogenic bacterium isolated from peatland soil.

Some species of the genus Clostridium are efficient acetate producers and have been deemed useful for upgrading industrial biogas. An acetogenic, strictly anaerobic, Gram-stain-positive, subterminal endospore-forming bacterium designated strain PL3T was isolated from peatland soil enrichments with H2 and CO2. Cells of strain PL3T were 0.8-1.0×4.0-10.0 µm in size and rod-shaped. Growth of strain PL3T occurred at pH 6.0-7.5 (optimum, pH 7.0), at 20-40 °C (optimum, 30 °C) and with 0-1.5 % (w/v) NaCl (optimum, 0.5%). Biochemical analyses revealed that strain PL3T metabolized lactose, maltose, raffinose, rhamnose, lactic acid, sorbitol, arabinose and glycerol. Acetic acid was the predominant metabolite under anaerobic respiration with H2/CO2. The major cellular fatty acids were C16 : 0, C16 : 1 cis 9 and C17 : 0 cyc. The main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, aminolipid and aminophospholipid. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain PL3T belongs to the genus Clostridium with the highest sequence similarity to Clostridium aciditolerans DSM 17425T (98.6 %) followed by Clostridium nitrophenolicum (97.8 %). The genomic DNA G+C content of strain PL3T was 31.1 mol%.The genomic in silico DNA-DNA hybridization value between strain PL3T and C. aciditolerans DSM 17425T was 25.1 %, with an average nucleotide identity of 80.2 %. Based on phenotypic, chemotaxonomic and phylogenetic differences, strain PL3T was suggested to represent a novel species of the genus Clostridium, for which the name Clostridium thailandense sp. nov. is proposed. The type strain is PL3T (=DSM 111812T=TISTR 2984T).

Morphology, Mechanical, and Water Barrier Properties of Carboxymethyl Rice Starch Films: Sodium Hydroxide Effect.

Carboxymethyl rice starch films were prepared from carboxymethyl rice starch (CMSr) treated with sodium hydroxide (NaOH) at 10-50% w/v. The objective of this research was to determine the effect of NaOH concentrations on morphology, mechanical properties, and water barrier properties of the CMSr films. The degree of substitution (DS) and morphology of native rice starch and CMSr powders were examined. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC) were used to investigate the chemical structure, crystallinity, and thermal properties of the CMSr films. As the NaOH concentrations increased, the DS of CMSr powders increased, which affected the morphology of CMSr powders; a polyhedral shape of the native rice starch was deformed. In addition, the increase in NaOH concentrations of the synthesis of CMSr resulted in an increase in water solubility, elongation at break, and water vapor permeability (WVP) of CMSr films. On the other hand, the water contact angle, melting temperature, and the tensile strength of the CMSr films decreased with increasing NaOH concentrations. However, the tensile strength of the CMSr films was relatively low. Therefore, such a property needs to be improved and the application of the developed films should be investigated in the future work.

Kinetics of Whole Cells and Ethanol Production from Candida tropicalis TISTR 5306 Cultivation in Batch and Fed-batch Modes Using Assorted Grade Fresh Longan Juice.

The kinetic profiles of Candida tropicalis TISTR 5306 cultivation based on modified yeast-malt (MYM), assorted grade fresh longan juice (AsgLG) and longan solid waste extract (LSWE) medium were evaluated in 1 l batch mode. The highest ethanol concentration level (25.5 ± 0.8 g/l) and ethanol yield - Yp/s of 0.491 ± 0.017 g ethanol/g consumed substrate, dried biomass concentration level (9.44 ± 0.05 g/l) and dried biomass yield - Yp/s of 0.533 ± 0.170 g dried biomass/g consumed substrate, specific pyruvate decarboxylase (PDC) activity (0.037 ± 0.003 U/mg protein) were achieved (p ≤ 0.05) in AsgLG medium. Scores ranking strategy were employed and AsgLG medium was subsequently selected with in the highest total score (p ≤ 0.05) of 698 ± 7 at 48 h. The cultivation in fed-batch mode with three rounds of pulse feeding (PF) in 1 l AsgLG medium was carried out. The apparent highest ethanol and dried biomass concentration levels with corresponding yields relative to time zero were (28.3 ± 0.5 g/l, 0.482 ± 0.012 g/g) at 120 h of PF2 and (9.39 ± 0.04 g/l, 0.110 ± 0.001 g/g) at 192 h of PF3. The maximum specific PDC activity was 0.057 ± 0.006 U/mg protein during PF1 feeding.

Photoautotrophic and Mixotrophic Cultivation of Polyhydroxyalkanoate-Accumulating Microalgae Consortia Selected under Nitrogen and Phosphate Limitation.

Microalgae consortia were photoautotrophically cultivated in sequencing batch photobioreactors (SBPRs) with an alteration of the normal growth and starvation (nutrient limitation) phases to select consortia capable of polyhydroxyalkanoate (PHA) accumulation. At the steady state of SBPR operation, the obtained microalgae consortia, selected under nitrogen and phosphate limitation, accumulated up to 11.38% and 10.24% of PHA in their biomass, which was identified as poly(3-hydroxybutyrate) (P3HB). Photoautotrophic and mixotrophic batch cultivation of the selected microalgae consortia was conducted to investigate the potential of biomass and PHA production. Sugar source supplementation enhanced the biomass and PHA production, with the highest PHA contents of 10.94 and 6.2%, and cumulative PHA productions of 100 and 130 mg/L, with this being achieved with sugarcane juice under nitrogen and phosphate limitation, respectively. The analysis of other macromolecules during batch cultivation indicated a high content of carbohydrates and lipids under nitrogen limitation, while higher protein contents were detected under phosphate limitation. These results recommended the selected microalgae consortia as potential tools for PHA and bioresource production. The mixed-culture non-sterile cultivation system developed in this study provides valuable information for large-scale microalgal PHA production process development following the biorefinery concept.

Effect of Pectin/Nanochitosan-Based Coatings and Storage Temperature on Shelf-Life Extension of "Elephant" Mango (Mangifera indica L.) Fruit.

The aim of extending shelf-life and maintaining quality is one of the major issues regarding mango fruit preservation. The quality of mango fruits is greatly affected by postharvest factors, especially temperature and fruit treatment. In this study, the effect of coating and storage temperature on the characteristics of mango fruits was investigated. The mango fruits were immersed in different concentrations (1.5%, 2.0%, and 2.5%) of pectin/nanochitosan dispersion (with ratios of pectin:nanochitosan 50:50), and (0.75%, 1% and 1.25%) of nanochitosan dispersion and stored at 17, 25, and 32 °C for 24 days. Changes in fruit, including weight loss, firmness, color, chemical composition (such as the total soluble solids concentration (TSS)), total sugar, reducing sugar, titratable acidity (TA), and vitamin C were periodically recorded. The results indicated that the pectin/nanochitosan coating significantly prevented reductions in the fruit weight, firmness, TSS, TA, and vitamin C content. Additionally, pectin/nanochitosan at a low temperature (17 °C) had a greater positive effect on fruit shelf-life and weight maintenance than 25 and 32 °C. The coated mango fruits maintained good quality for 24 days at 17 °C, while coated fruits stored at 25 °C and 32 °C, as well as uncoated ones stored at 17 °C, were destroyed after two weeks. At the maximum storage time evaluated, the coating formulations containing pectin and nanochitosan exhibited microbial counts below the storage life limit of 106 CFU/g of fruit. In general, the results showed that the pectin/nanochitosan coating (2%) with a storage temperature of 17 °C is the most effective strategy for improving quality and extending the shelf-life of mango fruits.