Recovering Apple Agro-Industrial Waste for Bioethanol and Vinasse Joint Production: Screening the Potential of Chile

Apple Waste/By-Products and Microbial Resources to Promote the Design of Added-Value Foods: A Review

Apple fruit is among the most consumed fruits in the world, both in fresh and processed forms (e.g., ready-to-eat fresh slices, juice, jam, cider, and dried slices). During apple consumption/processing, a significant amount of apple residue is discarded. These residues can also be interesting materials to exploit, particularly for direct valorization in the design of added-value foods. In fact, apple waste/by-products are rich in essential components, including sugars, proteins, dietary fibers, and phenolic compounds, as they comprise apple peels, seeds, and pulp (solid residue of juice production). In this sense, the current review paper presents an overview of the nutritional composition of apple waste/by-products, and mainly apple pomace, highlighting their application in producing value-added products through microbial biotechnology. If appropriately managed, apple by-products can generate a variety of useful compounds required in food (as well as in feed, pharmaceutics, and bioenergy). Recent strategies for the synergic use of apple waste/by-products and microbial resources such as lactic acid bacteria and yeasts are discussed. This review contributes to defining a reference framework for valorizing apple waste/by-products from a circular economy perspective through the application of bioprocesses (e.g., fermentation), mainly oriented towards designing foods with improved quality attributes.

Promising superabsorbent hydrogel based on carboxymethyl cellulose and polyacrylic acid: synthesis, characterization, and applications in fertilizer engineering

The combination of hydrogel and fertilizer as slow release fertilizer hydrogel (SRFH) has become one of the most promising materials to overcome the shortcomings of conventional fertilizer by decreasing fertilizer loss rate, supplying nutrients sustainably, and lowering the frequency of irrigation. The hydrogel based on carboxymethyl cellulose (CMC) and polyacrylic acid (PAA) (CMC/PAA) was synthesized. All materials, Vinasse, hydrogel (CMC/PAA) and (Vinasse/CMC-PAA) were characterized by FTIR, XRD, and SEM. The formed hydrogel was applied to control the salinity of Vinasse to use it as a cheap and economical fertilizer. The results showed that using the prepared hydrogel with Vinasse (V/CMC-PAA) as a slow-release organic fertilizer decreased the EC value through the first six hours from 1.77 to 0.35 mmohs/cm. Also, using V/CMC-PAA can control and keep the potassium as fertilizer for 50 days. The productivity per feddan from the sugar cane crop increased by about 15%, and the number of irrigations decreased from 5 to 4 times.

Apple pomace as an alternative substrate for butanol production

Butanol-producing strains Clostridium sp. UCM B-7570 and C. acetobutylicum UCM B-7407 were used for research from "Collection of strains of microorganisms and plant lines for food and agricultural biotechnology" of the Institute of Food Biotechnology and Genomics of the National Academy of Sciences of Ukraine, glycerol (BASF, Germany) and apple pomace (total moisture 4%) after apple juice production. The aim of this work was to study the possibility of using apple pomace by domestic butanol-producing strains of Clostridium sp. UCM B-7570 and C. acetobutylicum UCM B-7407 as a substrate. Producers were cultured on medium with different concentrations of apple pomace, glycerol was used for the inoculation. The presence of ethanol, acetone, and butanol in the culture liquid was determined using a gas chromatograph. It was determined that a significant part of the macrocomponent composition of the extracts can be used in bioconversion by producing strains of the genus Clostridium. It was determined that the highest concentration of butanol (10 g/dm3) was at a concentration of 120 g/dm3 in the extracts. The obtained data showed the possibility of using apple pomace as a substrate in biobutanol technology.

Evolution of physico-chemical parameters, microorganism diversity and volatile organic compound of apple pomace exposed to ambient conditions

In apple processing, waste material known as apple pomace amounts to 45% of production volumes. When this residue is stored in open-air for its stabilization and potential uses, Volatile Organic Compounds (VOCs) are produced, resulting in environmental and odor pollution, and must be managed to avoid their impact. This work aims to study the emission of VOCs utilizing TD-GC/MS and its relationship with changes in physico-chemical (moisture, pH, proteins, among others) and biological (bacteria and fungi using Illumina MiSeq) parameters under three environmental conditions: open-air (outdoors), under-roof (indoors) and oxygen-free. The 8-month study results showed a gradual increase in odorous VOCs and microbial diversity, a product of chemical and biological transformation processes in the samples. A 30% increase in odorant compounds responsible for the unpleasant smell was observed, especially esters, aldehydes and hydrocarbons in samples stored in oxygen-free and Open-air conditions. Increases in VOCs over time were associated with changes in physico-chemical and biological parameters, as well as fluctuations in environmental variables (temperature, relative humidity, and precipitation). The results of this research allow establishing a relationship between storage conditions and the production of VOCs. In addition, recommendations for waste storage time are provided for the most common uses of apple pomace based on the physico-chemical parameters observed, in order to avoid the generation of odorous compounds. Of all storage methods analyzed, under-roof is the most adequate in practice. This study's findings are pertinent for managing agribusiness waste and its potential environmental pollution.

Thermal Treatment to Obtain 5-Hydroxymethyl Furfural (5-HMF), Furfural and Phenolic Compounds from Vinasse Waste from Agave

Vinasses represent important final disposal problems due to their physical-chemical composition. This work analyzed the composition of tequila vinasses and increased 5-hydroxymethylfurfural, furfural, and phenolic compounds using thermal hydrolysis with hydrogen peroxide as a catalyst. A statistical Taguchi design was used, and a UPLC-MS (XEVO TQS Micro) analysis determined the presence and increase of the components. The treatment at 130 °C, 40 min, and 0.5% of catalyst presented the highest increase for 5-HMF (127 mg/L), furfural (3.07 mg/L), and phenol compounds as chlorogenic (0.36 mg/L), and vanillic acid (2.75 mg/L). Additionally, the highest removal of total sugars (57.3%), sucrose (99.3%), and COD (32.9%). For the treatment T130:30m:0P the syringic (0.74 mg/L) and coumaric (0.013 mg/L) acids obtained the highest increase, and the treatment T120:30m:1P increased 3-hydroxybenzoic (1.30 mg/L) and sinapic (0.06 mg/L) acid. The revaluation of vinasses through thermal treatments provides guidelines to reduce the impact generated on the environment.