Biobutanol production from coffee silverskin

Abstract

BackgroundCoffee silverskin, a by-product from coffee roasting industries, was evaluated as a feedstock for biobutanol production by acetone–butanol–ethanol fermentation. This lignocellulosic biomass contained approximately 30% total carbohydrates and 30% lignin. Coffee silverskin was subjected to autohydrolysis at 170 °C during 20 min, with a biomass-to-solvent ratio of 20%, and a subsequent enzymatic hydrolysis with commercial enzymes in order to release simple sugars. The fermentability of the hydrolysate was assessed with four solventogenic strains from the genus Clostridium. In addition, fermentation conditions were optimised via response surface methodology to improve butanol concentration in the final broth.ResultsThe coffee silverskin hydrolysate contained 34.39 ± 2.61 g/L total sugars, which represents a sugar recovery of 34 ± 3%. It was verified that this hydrolysate was fermentable without the need of any detoxification method and that C. beijerinckii CECT 508 was the most efficient strain for butanol production, attaining final values of 4.14 ± 0.21 g/L acetone, 7.02 ± 0.27 g/L butanol and 0.25 ± 0.01 g/L ethanol, consuming 76.5 ± 0.8% sugars and reaching a butanol yield of 0.269 ± 0.008 gB/gS under optimal conditions.ConclusionsCoffee silverskin could be an adequate feedstock for butanol production in biorefineries. When working with complex matrices like lignocellulosic biomass, it is essential to select an adequate bacterial strain and to optimize its fermentation conditions (such as pH, temperature or CaCO3 concentration).Electronic supplementary materialThe online version of this article (10.1186/s12934-018-1002-z) contains supplementary material, which is available to authorized users.

A global approach to obtain biobutanol from corn stover

“…In order to avoid inhibitory problems, it was decided to select the pretreatment conditions of 0.89% H2SO4 w/w, 125 °C and 5 min, because they offered acceptable sugar concentrations and low inhibitor concentrations. The total sugar concentration obtained (~40 g/L), moderate as it may seem, might guarantee successful ABE fermentations, as observed in previous works with cheese whey (Díez-Antolínez et al, 2016) or coffee silverskin (Hijosa-Valsero et al, 2018b), where initial sugar concentrations as low as 30-34 g/L enabled the generation of 7.0-8.5 g/L biobutanol. (Shaheen et al, 2000).…”

“…Then, 1.5 mL were mixed with 0.4 mL glycerol (80% v/v) in a cryogenic vial and stored at -80 °C until being used. Cellular reactivation and innocula preparation were performed in liquid RCM or in a potato based medium (in the case of DSM 2152 and DSM 792) as detailed by Hijosa-Valsero et al (2018b). Bacterial cultures were incubated for 20-48 h at 35 ºC in order to obtain a density of 5•10 8 cells/mL as determined by counting in a Bürker chamber (Paul Marienfeld GmbH & Co. KG, Lauda-Königshofen, Germany).…”

Engineering aspects of hydrothermal pretreatment: From batch to continuous operation, scale-up and pilot reactor under biorefinery concept

“…Besides the ethanol production from hydrothermal treated lignocellulosic biomass, this process had been used for the production of other biofuels such as butanol (Cebreiros et al, 2019). Recently, autohydrolyzed coffee silverskin for biobutanol production by acetonebutanol-ethanol fermentation using a Clostridium beijerinckii CECT 508 (Hijosa-Valsero et al, 2018). Overall, the hydrothermal pretreatment allows to be used alone or combined with other biotechnological processes (organosolv or alkali) to obtain a wide spectrum of manufacturing products (such as biofuels, chemicals and food additives) (Chen et al, 2016).…”

Characterization of Odor-Active Compounds, Polyphenols, and Fatty Acids in Coffee Silverskin

“…Coffee companies generate a significant amount of liquid and solid wastes (by-products); around 90% of the weight of coffee cherries (mostly pulp) is discarded during processing as agricultural waste or by-product [ 1 ]. Several authors have previously proposed different approaches to reuse the coffee by-products in order to reduce their disposal [ 2 , 3 , 4 , 5 , 6 , 7 ]. Among these by-products is coffee silverskin (CS), which is the major residue generated during the roasting process.…”