Process Optimization for Citrus Waste Biorefinery via Simultaneous Pectin Extraction and Pretreatment

Abstract

In a novel valorization approach for simultaneous pectin extraction and pretreatment (SPEP) of citrus waste (CW) by dilute nitric acid and ethanol, almost all of the CW was converted to bio-derived chemicals in a singlestep process at a low/moderate temperature. The SPEP was performed at different temperatures (70 °C and 80 °C), pH (1.8, 3.0, and 4.3), and extraction times (2 h and 3 h) with a full factorial design. The maximum pectin yield of 45.5% was obtained at pH 1.8, 80 °C, and 2 h. The pectin yields at pH 1.8 were much higher than at pH 4.3 and 3. Also, the degree of methyl-esterification at pH 1.8 was higher than 50%, whereas at the higher pH, low methoxyl pectins were extracted. The treated CW obtained after the SPEP, free from limonene, was subjected to separate cellulolytic enzymatic hydrolysis and ethanolic fermentation. The glucose yields in the enzymatic hydrolysates were higher for the CW treated at pH 1.8. The fermentation of the enzymatic hydrolysates by Mucor indicus resulted in fungal biomass yields in the range of 355 to 687 mg per g of consumed sugars. The optimum conditions for obtaining the maximum SPEP yield (glucose + pectin (g) / raw material (g))*100) were pH 1.8, 80 °C, and 2 h, which resulted in a yield of 58.7% (g/g CW).

Making Virtue Out of Necessity: Managing the Citrus Waste Supply Chain for Bioeconomy Applications

“…The percentage is more than 4% if one deals with the dried citrus waste [110]. Current research has shown a new technical process that increases the pectin yield from~40% of wet citrus waste to 58% [111]. The return from pastazzo in bran production for animal feed is more than it is for pectin production [110].…”

“…Pectin production from citrus waste is a relatively new route. During the past decade, several studies have investigated technology innovations to optimize the pectin yield [111,113]. The innovative process and the low return from pectin production could represent a huge barrier, even if there is a large demand for pectin in the market [82].…”

Application of Anaerobic Digestate as Inoculum for Treatment of the Plant-Derived Wastes: Case Study

“…The composition of total carbohydrates was similar in both sludges, while all other compounds were different. Activated sludge as well as other organic wastes "contain soluble sugars (mainly fructose, glucose, and sucrose), structural polysaccharides (cellulose, hemicelluloses, and pectin), lignin-like compounds (flavonoids), and essential oils" [42].…”

Making Virtue Out of Necessity: Managing the Citrus Waste Supply Chain for Bioeconomy Applications

“…The percentage is more than 4% if one deals with the dried citrus waste (Rezzadori et al, 2012). Current research has shown a new technical process that increases the pectin yield from ~40% of wet citrus waste to 58% (Satari et al, 2017). The return from pastazzo in bran production for animal feed is more than it is for pectin production (Rezzadori et al, 2012).…”

“…Pectin production from citrus waste is a relatively new route. During the past decade several studies have investigated technology innovations to optimize the pectin yield (Kim et al, 2004;Satari et al, 2017). The innovative process and the low return from pectin production could represent a huge barrier even if there is a large demand for pectin in the market (Bae et al, 2016).…”