Supercritical CO2 Extraction of Nannochloropsis sp.: A Lipidomic Study on the Influence of Pretreatment on Yield and Composition

Algal lipids have gained wide interest in various applications ranging from biofuels to nutraceuticals. Given their complex nature composed of different lipid classes, a deep knowledge between extraction conditions and lipid characteristics is essential. In this paper, we investigated the influence of different pretreatments on lipid extraction with supercritical CO2 by a lipidomic approach. Pretreatment was found to double the total extraction yield, thereby reaching 23.1 wt.% comparable to the 26.9 wt.% obtained with chloroform/methanol. An increase in acylglycerides was concurrently observed, together with a nearly doubling of free fatty acids indicative of partial hydrolysis. Moreover, an alteration in the distribution of glyco- and phospholipids was noted, especially promoting digalactosyldiglycerides and phosphatidylcholine as compared to monogalactosyldiglycerides and phosphatidylglycerol. At optimized conditions, supercritical CO2 extraction provided a lipid extract richer in neutral lipids and poorer in phospholipids as compared to chloroform/methanol, though with a very similar fatty acid distribution within each lipid class

Enzymatic production of pectic oligosaccharides from onion skins

Onion skins are evaluated as a new raw material for the enzymatic production of pectic oligosaccharides (POS) with a targeted degree of polymerization (DP). The process is based on a two-stage process consisting of a chelator-based crude pectin extraction followed by a controlled enzymatic hydrolysis. Treatment of the extracted crude onion skin's pectin with various enzymes (EPG-M2, Viscozyme and Pectinase) shows that EPG-M2 is the most appropriate enzyme for tailored POS production. The experiments reveal that the highest amount of DP2 and DP3 is obtained at a time scale of 75-90 min with an EPG-M2 concentration of 26 IU/mL. At these conditions the production amounts 2.5-3.0% (w/w) d.m for DP2 and 5.5-5.6% (w/w) d.m for DP3 respectively. In contrast, maximum DP4 production of 5.2-5.5% (w/w) d.m. is obtained with 5.2 IU/mL at a time scale of 15-30 min. Detailed LC-MS analysis reveals the presence of more methylated oligomers compared to acetylated forms in the digests

Continuous production of pectic oligosaccharides from sugar beet pulp in a cross flow continuous enzyme membrane reactor

Sugar beet pulp pectin is an attractive source for the production of pectic oligosaccharides, an emerging class of potential prebiotics. The main aim of the present work was to investigate a new process allowing to produce pectic oligosaccharides in a continuous way by means of a cross flow enzyme membrane reactor while using a low-cost crude enzyme mixture (viscozyme). Preliminary experiments in batch and semi-continuous setups allowed to identify suitable enzyme concentrations and assessing filtration suitability. Then, in continuous experiments in the enzyme membrane reactor, residence time and substrate loading were further optimized. The composition of the obtained oligosaccharide mixtures was assessed at the molecular level for the most promising conditions and was shown to be dominated by condition-specific arabinans, rhamnogalacturonans, and galacturonans. A continuous and stable production was performed for 28.5 h at the optimized conditions, obtaining an average pectic oligosaccharide yield of 82.9 ± 9.9% (w/w), a volumetric productivity of 17.5 ± 2.1 g/L/h, and a specific productivity of 8.0 ± 1.0 g/g E/h. This work demonstrated for the first time the continuous and stable production of oligosaccharide mixtures from sugar beet pulp using enzyme membrane reactor technology in a setup suitable for upscaling

Continuous production of pectic oligosaccharides from onion skins with an enzyme membrane reactor

The aim of this research was to valorize onion skins, an under-utilized agricultural by-product, into pectic oligosaccharides (POS), compounds with potential health benefits. To achieve high hydrolysis performance with the multi-activity enzyme Viscozyme L, an innovative approach was investigated based on a cross-flow continuous membrane enzyme bioreactor (EMR). The influence of the various process conditions (residence time, enzyme concentration, substrate concentration) was investigated on productivity and yield. The composition of the POS mixtures in terms of mono- and oligosaccharides was assessed at the molecular level. At optimized conditions, a stable POS production with 22.0 g/L/h volumetric productivity and 4.5 g/g POS/monosaccharides was achieved. Compared to previous results obtained in batch for the enzyme Viscozyme L, EMR provided a 3–5× higher volumetric productivity for the smallest POS. Moreover, it gave competitive results even when compared to batch production with a pure endo-galacturonase enzyme, demonstrating its feasibility for efficient POS production

Novel Intensified Back Extraction Process for Itaconic Acid: Toward in Situ Product Recovery for Itaconic Acid Fermentation

Itaconic acid (IA), an unsaturated dicarboxylic acid produced by fermentation, is a promising alternative to petrochemical-based monomers as a building block for plastics, resins, and synthetic fibers. Efficient recovery of IA from aqueous fermentation broth was previously achieved by amine-based reactive extraction (RE) systems. In the present work, several back extraction methods were tested in order to recover IA from four different RE solutions, three based on trioctylamine and the diluents methyloctanoate, pentylacetate, and 1-octanol, and one based on <i>N</i>-methyldioctylamine and the diluent 1-octanol. Conventional back extraction methods using a temperature swing, NaOH, or tertiary volatile amines were applied and tested at different conditions. Especially with tertiary volatile amines, good back extraction efficiencies were achieved. As an intensified approach, in addition a novel back extraction-conversion method was developed to recover the itaconic acid in the form of methyl-esters. This approach was based on noncatalyzed in situ esterification with high temperature–pressure methanol (HTPM) allowing a continuous processing. Reaction temperature, residence time, pressure, and methanol excess were investigated. At 200–250 °C and a residence time of 10–20 min, with methanol dosed at a similar weight as the RE-layer, ester formation of >80 mol % could be obtained with a continuous esterification process. This latter method can be a suitable alternative technique for standard back extraction procedures, aiming at an easy recovery of the IA ester through distillation, followed by a direct polymerization to bioplastics