Bioconversion of Grape Pomace with Rhizopus oryzae under Solid-State Conditions: Changes in the Chemical Composition and Profile of Phenolic Compounds

Abstract

Grape pomace is a sustainable source of bioactive phenolic compounds used in various industries. The recovery of phenolic compounds could be improved by biological pretreatment of grape pomace, as they are released from the lignocellulose structure by the activity of the enzymes produced. The influence of grape pomace pretreatment with Rhizopus oryzae under solid-state conditions (SSF) on the phenolic profile and chemical composition changes was studied. SSF was performed in laboratory jars and in a tray bioreactor for 15 days. Biological pretreatment of grape pomace resulted in an increase in the content of 11 individual phenolic compounds (from 1.1 to 2.5-fold). During SSF, changes in the chemical composition of the grape pomace were observed, including a decrease in ash, protein, and sugar content, and an increase in fat, cellulose, and lignin content. A positive correlation (r > 0.9) was observed between lignolytic enzymes and the hydrolytic enzyme’s xylanase and stilbene content. Finally, after 15 days of SSF, a weight loss of GP of 17.6% was observed. The results indicate that SSF under experimental conditions is a sustainable bioprocess for the recovery of phenolic compounds and contributes to the zero-waste concept by reducing waste.

In Vitro Bioaccessibility Assessment of Phenolic Compounds from Encapsulated Grape Pomace Extract by Ionic Gelation

“…The chemical composition of grape pomace, including the content of dry matter, free fats, crude proteins, ash, individual sugars, neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), total organic carbon (TOC, TOC LE ), and total nitrogen (TN), was determined according to the methods described by Šelo et al [ 1 ]. Table 4 shows the equations according to which the individual components of the chemical composition were calculated.…”

“…To determine the content of total phenolic compounds (TPC), total flavonoids (TFC), total extractable proanthocyanidins (TPA), and individual phenolic compounds (ICPs), a conventional solid-liquid extraction was performed according to Šelo et al [ 1 ]. Briefly, phenolic compounds were extracted from 1 g of grape pomace with 40 mL of 50% aqueous ethanol solution at 80 °C for 120 min at 200 rpm in a water bath with shaking (Julabo, SW-23, Seelbach, Germany).…”

“…It consists of the skins, seeds, pulp, and sometimes the stems of the grapes, which influence its chemical composition, rich in many different components such as sugars, fibers, fats, proteins, bioactive phenolic compounds, etc. [ 1 , 2 , 3 ]. Scientific interest in phenolic compounds from grape pomace is most prominent in the literature and has not diminished over the years, as they offer numerous benefits when used in the pharmaceutical, food, and cosmetic industries, or in medicinal applications.…”

Evaluation of Solid-State Fermentation Conditions from Pineapple Peel Wastes to Release of Bioactive Compounds by <em>Aspergillus niger </em>spp.

“…Currently, new environmentally friendly alternatives are being sought for obtaining polyphenolic compounds, among the alternatives are biotechnological ones such as fermentation, either in the solid state (which is considered as such because it is in the absence of water but at optimum moisture levels so that the microorganism can grow) [17,18] or fermentation in the liquid state, as its name suggests, is carried out in a liquid medium under certain conditions of pH, inoculum, oxygen and aeration; these biotechnological processes produce enzymes that help the release of polyphenolic compounds, which is why it is a promising alternative [18].…”

“…Although fermentation methods were already known, nowadays it has gained more interest due to its simplicity and proximity to the natural conditions of the microorganisms used, whether yeast or fungi [17]. Within the fermentation processes, agro-industrial waste have been used, since the aim is to make better use of these waste, such is the case of pineapple.…”