Interest in the development of bioprocesses for the production or extraction of bioactive compounds from natural sources has increased in recent years due to the potential applications of these compounds in food, chemical, and pharmaceutical industries. In this context, solid-state fermentation (SSF) has received great attention because this bioprocess has potential to successfully convert inexpensive agro-industrial residues, as well as plants, in a great variety of valuable compounds, including bioactive phenolic compounds. The aim of this review, after presenting general aspects about bioactive compounds and SSF systems, is to focus on the production and extraction of bioactive phenolic compounds from natural sources by SSF. The characteristics of SSF systems and variables that affect the product formation by this process, as well as the variety of substrates and microorganisms that can be used in SSF for the production of bioactive phenolic compounds are reviewed and discussed.

Bay leaves (BL) (Laurus nobilis L., Family: Laureceae) are traditionally used to treat some symptoms of gastrointestinal problems, such as epigastric bloating, impaired digestion, eructing and flatulence. These biological properties are mainly attributed to its phenolic compounds. In this paper, ultrasound-assisted extraction of phenolic compounds from Laurus nobilis L. (Laureceae) was studied. Effects of several experimental factors, such as sonication time, solid/liquid ratio and concentration of solvent on extraction of phenolic compounds were evaluated through a randomized complete block design with factorial treatment arrangement (3(3)). The best extraction conditions were: 1g plant sample with 12 mL of 35% ethanol, for 40 min, obtaining a yield of phenolic compounds of 17.32±1.52 mg g(-1) of plant. In addition, free radical-scavenging potential of DPPH and lipid oxidation inhibition, by linoleic acid peroxidation of the selected extract was measured in order to evidence their antioxidant properties. Results indicated that high amounts of phenolic compounds can be extracted from L. nobilis by ultrasound-assisted extraction technology.

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Agro-industrial byproducts represent a serious environmental problem and the industries producing these residual materials have incurred expenses for their proper disposal and generally increase the pollution due to the high content of organic substances and might represent legal problems. However, the residues such as grape wastes are potential source of phenolic compounds which are widely known for their high antioxidant activity. Bioprocesses such as enzyme technology represent an alternative for production of those bioactive compounds from agro-industrial byproducts. In this study, different types of commercial enzymes such as Celluclast® 1.5 L, Pectinex® Ultra and Novoferm® were used to release phenolic compounds from grape wastes. The hydrolysates were analyzed in their total phenolic compounds and antioxidant activity with Folin–Ciocaletu test and DPPH· radical-scavenging assay, respectively. A good correlation was obtained between antioxidant activity and phenolics released. The highest antioxidant activities registered were 86.8 ± 0.81, 82.9 ± 0.31 and 90 ± 0.37 % at 12 h for Celluclast® 1.5 L, Pectinex® Ultra and Novoferm®, respectively. Novoferm® had the strongest effect on phenolic release from grape waste, followed by Pectinex® Ultra and Celluclast® 1.5 L. High performance liquid chromatography–electrospray–mass spectrometry clearly revealed that the increment of antioxidant activity is associated with the release of O-coumaric acid.

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Stability of the total phenolic content, ascorbic acid, total carotenoids and antioxidant activity in eight fruit beverages was analyzed. The influence of storage temperature (4, 8 and 11 °C) during the product shelf-life (20 days) was evaluated. Pomegranate Juice presented the highest values for antioxidant activity by DPPH• assay (552.93 ± 6.00 GAE μg mL−1), total carotenoids (3.18 ± 0.11 βCE μg mL−1), and total phenolic content (3967.07 ± 2.47 GAE μg mL−1); while Splash Blend recorded the highest levels of ascorbic acid (607.39 ± 2.13 AAE μg mL−1). The antioxidant capacity was stable at 4 and 8 °C for the first 8 days of storage; while carotenoids and ascorbic acid were slightly degraded through the storage time, possibly due to oxidation and/or reactions with other compounds. The results suggest that the observed variation during testing could be related to storage conditions of the final product.

Several plants that are rich in polyphenolic compounds and exhibit biological properties are grown in the desert region of Mexico under extreme climate conditions. These compounds have been recovered by classic methodologies in these plants using organic solvents. However, little information is available regarding the use of alternative extraction technologies, such as ultrasound. In this paper, ultrasound-assisted extraction (UAE) parameters, such as the liquid:solid ratio, solvent concentration and extraction time, were studied using response surface methodology (RSM) for the extraction of polyphenols from desert plants including Jatrophadioica,Flourensiacernua, Turneradiffusa and Eucalyptuscamaldulensis. Key process variables (i.e., liquid:solid ratio and ethanol concentration) exert the greatest influence on the extraction of all of the phenolic compounds (TPC) in the studied plants. The best conditions for the extraction of TPC involved an extraction time of 40min, an ethanol concentration of 35% and a liquid:solid ratio ranging from 8 to 12mlg(-1) depending on the plant. The highest antioxidant activity was obtained in the E. camaldulensis extracts. The results indicated the ability of UAE to obtain polyphenolic antioxidant preparations from desert plants.