Recovering rhamnogalacturonan-I pectin from sugar beet pulp using a sequential ultrasound and microwave-assisted extraction: Study on extraction optimization and membrane purification.

This research focuses on the integrated recovery of rhamnogalacturonan-I (RG-I) pectin from sugar beet pulp (SBP). First, the extraction of RG-I pectin through sequential ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) was assessed. Optimization using a response surface methodology identified the optimal conditions as initial pH 4, 10 min of UAE, and 157 °C for MAE, achieving a 66.0 % recovery of pectooligosaccharides (POS). Additionally, purification through continuous diafiltration and concentration via ultrafiltration of the POS using membranes with different molecular weight cut-offs (MWCO) was explored. In contrast to previous research using discontinuous diafiltration, the use of continuous diafiltration allowed a decrease in the extract viscosity and obtained higher yields using a higher MWCO membrane. The refined RG-I pectin solids exhibited a high global yield (39-40 g pectin/100 g SBP), and high-methoxyl characteristics, as well as purity levels (70-80 %) similar to commercial prebiotics.

Efficient biobutanol production by acetone-butanol-ethanol fermentation from spent coffee grounds with microwave assisted dilute sulfuric acid pretreatment.

The integral valorization of potential sugars (cellulosic and hemicellulosic) from spent coffee grounds (SCG), a lignocellulosic residue, is proposed in this work. With this aim, the microwave assisted dilute sulfuric acid pretreatment has been optimized, leading to a hemicellulosic sugar recovery in the pretreatment liquid (HSRL) and an enzymatic hydrolysis yield of 79 and 98%, respectively, at 160.47 °C and 1.5% H2SO4. Moreover, the complete digestibility of cellulose (enzymatic hydrolysis yield = 100%) was also discovered for non-pretreated SCG, which is very interesting. Secondly, the production of biobutanol, an advanced biofuel, is also proposed from pretreated SCG enzymatic hydrolysate and pretreatment liquid achieved under optimal conditions. These were fermented by Clostridium beijerinckii, yielding 95 kg butanol/t SCG (dry matter) and 151 kg acetone-butanol-ethanol/t SCG (dry matter).

Efficient acetone-butanol-ethanol production by Clostridium beijerinckii from sugar beet pulp.

Sugar beet pulp (SBP) has been investigated as a promising feedstock for ABE fermentation by Clostridium beijerinckii. Although lignin content in SBP is low, a pretreatment is needed to enhance enzymatic hydrolysis and fermentation yields. Autohydrolysis at pH 4 has been selected as the best pretreatment for SBP in terms of sugars release and acetone and butanol production. The best overall sugars release yields from raw SBP ranged from 66.2% to 70.6% for this pretreatment. The highest ABE yield achieved was 0.4g/g (5.1g/L of acetone and 6.6g/L butanol) and 143.2g ABE/kg SBP (62.3g acetone and 80.9g butanol) were obtained when pretreated SBP was enzymatically hydrolyzed at 7.5% (w/w) solid loading. Higher solid loadings (10%) offered higher acetone and butanol titers (5.8g/L of acetone and 7.8g/L butanol). All the experiments were carried out under not-controlling pH conditions reaching about 5.3 in the final samples.

Production of biomass by Spirulina maxima using sugar beet vinasse in growth media.

Cultivation of Spirulina maxima in media containing vinasse from beet molasses fermentation has been studied in both batch cultures and a photobioreactor. The results obtained in batch tests showed that S. maxima was able to grow in Schlösser media containing up to 5 g/L of vinasse or alkaline diluted vinasse (5 g/L). Biomass concentrations ranging from 3.5 and 4.8 g/L, productivities from 0.15 to 0.24 (g/L d) and specific growth rates about 0.1 d⁻¹ were found. Betaine, an organic nitrogenous compound present in vinasse, was completely consumed. The continuous operation in a tubular photobioreactor with Schlösser medium supplemented with 2g/L of vinasse led to S. maxima concentrations about 8 g/L and productivities of 0.7 g/L d for an hydraulic retention time of 11 d using a light intensity of 3000 lux, slightly higher than those achieved with Schlösser medium, showing that the addition of vinasse presents a positive effect on the growth of the microalgae.