Xylitol Production from Exhausted Olive Pomace by Candida boidinii

Abstract

In this work, the production of xylitol from a hemicellulosic hydrolysate of exhausted olive pomace (EOP), a residue originated in the olive oil production process by Candida boidinii, was assessed. The hydrolysate was obtained by dilute acid pretreatment of EOP at 170 °C and 2% H2SO4 (w/v). A previous detoxification step of the hydrolysate was necessary, and its treatment with activated charcoal and ion-exchange resin was evaluated. Prior to fermentation of the hydrolysate, fermentation tests in synthetic media were performed to determine the maximum xylitol yield and productivity that could be obtained if inhibitory compounds were not present in the medium. In addition, the glucose existing in the media exerted a negative influence on xylitol production. A maximum xylitol yield of 0.52 g/g could be achieved in absence of inhibitor compounds. Fermentation of the hemicellulosic hydrolysate from EOP after detoxification with ion-exchange resin resulted in a xylitol yield of 0.43 g/g.

Valorisation of Exhausted Olive Pomace by an Eco-Friendly Solvent Extraction Process of Natural Antioxidants

“…For instance, Manzanares et al [20] studied different hydrothermal pretreatments for sugar recovery from both the cellulose and hemicellulose fractions of this waste. López-Linares et al [21] reported a bioconversion process for EOP hemicellulosic sugars into ethanol by fermentation with Escherichia coli; also, the production of xylitol from a hemicellulosic hydrolysate of EOP by Candida boidinii was evaluated [22]. According to Albahari et al [23], the valorisation of the olive oil byproducts is extremely interesting, although it should be based on sustainable principles and green chemistry.…”

High level xylitol production by Pichia fermentans using non-detoxified xylose-rich sugarcane bagasse and olive pits hydrolysates

“…As a result of it, a small quantity of xylitol is funnelled into cell metabolism, and more is pumped out into extracellular environment ( Tochampa et al, 2005 , Wannawilai et al, 2017 ). Glucose/xylose ratios > 10% have been reported to negatively impact the transport of xylose and inhibit the action of XR and a ratio less than or equal to 10% could enhance the enzymatic action ( López-Linares et al, 2020 , Tochampa et al, 2005 ).…”

“…There is substantial literature available on SCB-based xylitol accumulation but scarce on xylitol production using waste streams from olive industries. Recently, López-Linares et al (2020) evaluated xylitol production from hemicellulosic hydrolysate of exhausted olive pomace (EOP) by Candida boidinii NCAIM Y.01308. EOP is obtained as a solid residue after extraction of the remaining oil present in the olive pomace with hexane and contains cellulose, hemicellulose, lignin, and extractives.…”

“…Xylitol being a sugar alcohol at high concentration causes high oxidative stress and affect cell membrane fluidity resulting in reduced xylose assimilation rate ( Kim et al, 2002 ). The difference in the titers and yield between the pure sugars and the hydrolysates may be due to presence of fermentation inhibitors like acetic acid, metal ions, lignin derivatives and other undetected ions or chemicals ( Ping et al, 2013 , López-Linares et al, 2020 ).

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Fruit pomace-lignin as a sustainable biopolymer for biomedical applications

“…The study was able to show that the valorization of grape pomace had the potential to present significant economic benefits with a scaled-up pomace valorization plant characterized by a net present value of US$ 111.7 ×10 6 . Other studies have investigated WP conversion to valuable chemicals such as Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate), xylitol, polyhydroxyalkanoates, levulinic acid, and n-Butyl levulinate (Antonetti et al, 2020;Kovalcik et al, 2020;López-Linares et al, 2020;Martinez et al, 2016). Based on the studies presented above, the valorization of WP has so far focused on the optimized recovery of carbohydrate forms before their conversion to bioproducts (i.e.…”