Side Stream Research Articles

From molasses to purified α-ketoglutarate with engineered Corynebacterium glutamicum

α-ketoglutarate (AKG) is a valuable dicarboxylic acid with multiple applications in the food, pharmaceutical and chemical industries. Its chemical synthesis is associated with toxic by-products, low specificity and high energy input. To create a more environmentally friendly and sustainable alternative, a microbial production process for AKG was developed. Four potential producer strains were generated by metabolic engineering of Corynebacteriumglutamicum and characterized on defined glucose/sucrose media as well as molasses, a side stream from sugar beet processing. While strain C.glutamicum PO6-iolT1Δgdh ΔgltB mscCG’ ΔodhA was not able to grow on defined media it outperformed all predecessor variants on molasses. Successful scale-up into a fed-batch bioreactor process with molasses yielded 96.2 g AKG with a conversion yield of 0.64 gg−1. Finally, downstream processing by liquid–liquid extraction with ethyl acetate enabled product purification with an extraction efficiency of 87 % and an AKG purity of > 93 %.

Combined thermochemical-biotechnological approach for the valorization of polyolefins into polyhydroxyalkanoates: Development of an integrated bioconversion process by microbial consortia

Waste management of persistent polymers such as polyolefins (PO)1 still represents a major challenge, often leading to material loss from the value chain and contributing to plastic pollution. This study investigated an integrated process to valorize PO pyrolysis side stream. PO wax was recovered and used as a feedstock for a microbial bioconversion process. A modified emulsification protocol (using two-surfactants system) allowed the successful dispersion and bioconversion of PO wax without the need of the extra oxidation step. Enrichment of plastic landfill inocula allowed to develop efficient mixed microbial consortia (MMC) able to grow on PO wax. Adaptive laboratory evolution improved 4 times cell growth, leading to 2.6–17.3 times shorter lag phase. The bioconversion process using the adapted MMC was performed in a 2 L-bioreactor with PO wax-emulsified media (10 g L−1) at neutral pH and 20% pO2. 87% of substrate was consumed within 12 h and complete consumption was achieved within 48 h (4 times faster than previously reported). A maximum of 2.95 gCDW L−1of biomass was produced, while the intracellular triglycerides reached a maximum of 105.5 mg L−1 at 30 h. Moreover, the conversion of PO wax into polyhydroxyalkanoates (PHAs) was demonstrated and the production was maximized by statistical optimization. Maximum PHA titer of 384 0.1 mg L−1 was achieved, which represents a 1.5–17 times improvement from previous reports. This integrated thermochemical-biotechnological approach might represent an interesting strategy to valorize and upcycle currently unrecyclable PO-rich mixed plastic waste streams, thus improving the circularity of the plastic sector.

Textured vegetable protein from flaxseed press cake and pea – syntonizing chemical and structural properties

Flaxseed press cake (FS) was mixed with pea protein isolate and low-moisture twin-screw-extruded to valorize the oil production side stream as meat analogue. Water input, FS content, barrel temperature, and throughput were varied in a Box-Behnken design to test these factors’ influences on extrusion response parameters (pressure, temperature, mechanical energy input), lipid oxidation product and process contaminant formation (by liquid chromatography and head-space gas chromatography mass spectrometry), and mechanical properties of the TVPs.The water input was identified as the strongest influencing factor, reducing shear forces in the extruder and thereby reducing mechanical energy input, pressure, and temperature and affecting several TVP properties. Volatile lipid oxidation products from enzymatic oxidation in the raw materials are decomposed and steam-stripped during extrusion. Higher melt temperatures and lower water contents enhance this effect and promote the formation of masking “roasted” flavour compounds. However, acrylamide (<100 µg/kg) and trans-fatty acids (<0.4 g/kg) are also formed under flavour-improving conditions and TVP hardness is reduced. FS increases TVP density and reduces expansion and hardness. Reconciling mitigation of undesired chemical compounds and meat-like mechanical properties (at 16-18% water, 55-65% FS, mass flows <8 kg/h), a FS-based TVP can be created, combining nutritional and sustainability benefits of FS.

Techno-economic analysis and optimisation of Piperazine-based Post-combustion carbon capture and CO2 compression process for large-scale biomass-fired power plants through simulation

This study aims to investigate a cost-effective and energy-efficient amine-based post-combustion carbon capture (PCC) process for large-scale supercritical biomass-fired power plants (SC BFPP). Thus, we have quantified the energy and economic performance of the PCC process with different configurations and solvents. Three process configurations which included the standard configuration, the absorber intercooler (AIC) with the advanced flash stripper (AFS) and the AIC, AFS and side stream extraction (SSE) were simulated in Aspen Plus® V11 using 30 wt% and 40 wt% piperazine (PZ) as solvent. In addition to this, CO2 compression trains using the heat pump (HP) and supercritical CO2 cycle (s-CO2) were also simulated. Sensitivity analysis of the PCC process was carried out to investigate the impact of important parameters on the energy performance of the process. Furthermore, energy analysis shows that a minimum energy consumption of 2.78 GJ/tCO2 was achieved with the PCC process using 40 wt% PZ, a combination of the AIC, AFS and SSE for capture and s-CO2 for compression. This achieved a significant energy saving of 1.01 GJ/tCO2 compared with the standard PCC process using 30 wt% monoethanolamine that is used as the benchmark in this study. The economic analysis results showed that the minimum CO2 capture cost of 55.70 $/tCO2 was achieved using the AIC-AFS-SSE-sCO2 configuration and 40 wt% PZ as solvent. This represents a 19.5 % reduction in cost compared with the standard 40 wt% PZ process with a cost of 69.18 $/tCO2. The optimisation of the PZ-based PCC process was carried out to determine the optimal solvent concentration with the minimum carbon capture cost. It was found that the optimal PZ concentration for the PCC process based on standard and AFS configurations were 37.5 wt% and 32.5 wt%, respectively. The optimisation of the stripper pressure for the minimum carbon capture cost was conducted. As a result, compared with the standard PCC process using 40 wt% PZ, the energy consumption and CO2 capture cost of the optimised process at the suggested pressure of 7 bar were reduced by 41.6 % and 32.4 %, respectively.

Dynamic modeling and modification of ternary semicontinuous distillation without a middle vessel for improved controllability and energy performance

Ternary distillation conventionally requires two sequential columns. In a process intensification technique, the second column is eliminated by operating the first column in a cyclic manner, where the intermediate component is withdrawn periodically from a side stream. This process, called semicontinuous distillation (SCD) without a middle vessel, can lower the separation costs significantly. However, it exhibits controllability challenges due to the periodic recycling of the side stream. In this work, the process controllability is improved by adding a surge tank in the side stream recycle path. The modification increases significantly the process robustness without changing the operation recipe. Also, the modified SCD can lower maintenance costs as the manipulated variables experience milder oscillations. Moreover, it is shown to have a faster startup than the original design, yielding about 13 % energy saving per feed processed and processing about 25 % more feed during the startup compared with the original design. The case studies show the surge tank volume should be chosen based on the trade-off between attenuation of undesired disturbances and slow-down of desired control actions. Also presented in this article is detailed hybrid discrete-continuous dynamic modeling of the SCD and how the resulting model is implemented in the open-source software OpenModelica.

Leveraging side-stream sludge fermentation for phosphorus recovery in wastewater treatment systems

This study proposes the integration of a new P-recovery strategy through the use of a side stream enhanced biological P removal (S2EBPR) process. To evaluate this alternative, a 150 L pilot-scale anaerobic/anoxic/aerobic (A2O) plant was operated with a side-incorporated reactor (10 or 23 L) to work as an anaerobic side stream sludge fermenter (SSSF). The P removal performance and possible P-recovery under different hydraulic residence time in the SSSF were evaluated. The integration of the SSSF in the A2O configuration provided an excellent 98 % P-removal and allowed to create in the SSSF a stream with a very high soluble phosphate concentration (up to 196.5 ± 10.9 mgP/L). The supernatant of the wasted activated sludge (WAS) discharged from the SSSF contained as soluble phosphate up to 40 % of the total P input to the plant.

Pentacyclic Triterpenoid Content in Cranberry Raw Materials and Products

Cranberry fruit extracts have been shown to inhibit expression of pro-inflammatory cytokines in THP-1 cells and reduce colonic tumor burden and tissue inflammation in a mouse model of colitis. These activities are attributed to both the triterpenoid and polyphenol constituents of the fruit. The pentacyclic triterpenoids ursolic acid (UA), oleanolic acid (OA), corosolic acid (CA), maslinic acid (MA), and esters of UA and OA occur in the waxy layer of cranberry peel, and their content in cranberry products is likely to vary with the fruit source and processing methods. UPLC-MS (ultra performance liquid chromatography-mass spectrometry) was applied to determine the four triterpenoid acids and their esters in cranberry products and raw materials. Cranberry pomace, a side stream in juice production, was a rich source at 64,090 µg total triterpenoids/g DW. Cranberry juice beverages ranged from 0.018 to 0.26 µg/g of product, fruit samples ranged from 6542 to 17,070 µg/g DW, and whole berry products contained up to 2665 µg/g DW. Free UA was the most plentiful triterpenoid in all samples. These analyses illustrate the potential value of an underutilized side stream in cranberry juice production and highlight potential benefits of whole fruit products.

The industrial application potential of sugar beet pulp derived monosaccharides d-Galacturonic acid and l-Arabinose.

This review provides a perspective on the industrial application potential of sugar beet pulp (SBP) derived monosaccharides. The broad application of these monosaccharides could contribute to bio-based alternatives and sustainable practices, essential for the transition towards a more circular economy. This review focuses on the utilization and application of two SBP monosaccharides, d-galacturonic acid (d-GalA) and l-arabinose (l-Ara), derived from pectin and hemicellulose. These polysaccharides are major components of sugar beet pulp, an important side stream of sucrose production. d-GalA and l-Ara are therefore abundant in biomass and offer unique molecular structures amenable to selective chemical or enzymatic modifications. We review their application in various industrial applications such as the development and production of bioactive compounds, home and personal care products, and other industries.

Identification of molecules from tomato plant residues using sustainable green chemicals

AbstractHigh quantities of biomass produced in greenhouses create environmental problems as this side stream, and its downgraded products are not further used in the production cycle. The aim of our research was the identification and semi-quantification of molecules extracted from vegetative tomato plant residues with sustainable green alternative solvents using vacuum-assisted soxhlet and solid–liquid extraction to evaluate the possibilities for high-value applications for the first time. To identify compounds, gas chromatography–mass spectrometry (GC–MS) analysis and the Folin–Ciocalteau method were used. In sum, 285 different compounds have been assigned to 383 detected peaks using GC–MS analysis. The solvents 2-methyltetrahydrofuran (2-MTHF) and ethyl acetate, compared with ethanol and hexane, provided better results with a maximum number of 99 ± 8.83 compounds, a maximum total concentration of 5894.82 ± 586.48 and 3363.02 ± 71.14 mg naphthalene equivalent (NEQ) kgdw−1, and a total phenolic content of 2143.25 ± 155.17 and 1605.92 ± 66.46 mg gallic acid equivalent (GAE) kgdw−1, respectively. With 781.2 ± 112.66 and 718.25 ± 54.89 mg NEQ kgdw−1, the compound neophytadiene was the most common terpene in ethyl acetate and 2-MTHF extracts, respectively. It can be concluded that vegetative tomato plant residues contain a large variety of bioactive molecules. Green solvents, such as 2-MTHF and ethyl acetate, enhance the extraction of these molecules from the solid matrix. Graphical abstract

Microscopic study of proteins, starch and cell walls in potato trimmings

Potato trimmings are an undervalued food industry by-product and represent a potential source of valuable nutrients such as potato proteins. Cryo-scanning electron microscopy, atomic force microscopy, fluorescence microscopy and Raman microscopy were used to define the structural organisation of the protein fraction in this food side stream. The complementarity of the techniques allowed to localise the proteins in potato trimmings but also revealed the microstructure of these proteins, which were mainly present as aggregates in the cytoplasm, near starch granules and within gelatinised starch. Globules in the aggregates ranged in size from 0.1 to 0.25 μm. Upon acid-based stabilisation, differences in the microstructure of both gelatinised starch and cell walls were observed. These were most apparent in samples stabilised by steered fermentation, and it is suggested that these changes have caused the improved protein extractability (+41%) observed in these samples. A multipronged microscopy approach helps to elucidate the impact of acid-based stabilisation techniques and might explain the positive effect of the stabilisations on protein extractability.

Potato and dairy industry side streams as feedstock for fungal and plant cell cultures

Utilization of industrial side streams as nutrient source for cellular agriculture is a promising option to improve the sustainability of the production processes. The aim of the study was to evaluate usability of two liquid food industry side streams, potato cell fluid and acid whey, as nutrient source for production of food ingredients with plant cell cultures (arctic bramble (Rubus arcticus L.) and tobacco BY-2 (Nicotiana tabacum L.)) and filamentous fungi (Paecilomyces variotii, Rhizopus oligosporus and Trichoderma reesei). The side streams were found to contain various sugars and other potential nutrients suitable for the studied organisms. The side streams were used as a sole nutrient source (fungi) or as a replacement of selected nutrients in the growth media (fungi and plant cells) in flask scale cultivations. Acid whey was successfully used as a growth medium for filamentous fungi, but it inhibited plant cell growth presumably due to high organic acid content (14 g/l). Potato side stream was found suitable as a fungal and plant cell growth media supplement, and it was used together with glucose for filamentous fungi, or as a partial replacer of macronutrients for plant cells, in bioreactor cultivations yielding high fungal (up to 36 g/l dry weight) and good plant cell (9.5 g/l dry weight) biomass production. Analyses of the produced biomasses revealed good nutritional value in terms of amino acid (17–27 % of dry matter) and dietary fiber (23–30 % of dry matter) contents, giving good premises for utilization in human nutrition.

Sustainable and efficient separation of ternary multi-azeotropic mixture butanone/ethanol/water based on the intensified reactive extractive distillation: process design, multi-objective optimization, and multi-criteria decision-making

It is of great significance and necessity to develop a sustainable and efficient separation scheme of butanone (MEK), ethanol (EtOH), and water, which are usually formed during the cinepazide maleate synthesis process. To the best of our knowledge, the systematic separation of this ternary multi-azeotropic mixture remains comparatively less studied, compounded by the significant challenges posed by its intricate composition comprising four azeotropes and three distillation boundaries. Therefore, a systematic approach by integrating the process design, multi-objective optimization, and multi-criteria decision-making (MCDM) methods was proposed to achieve the sustainable separation. Initially, three separation schemes, i.e., triple-column extractive distillation (TCED), double-column reactive extractive distillation (DCRED), and side stream intensified double-column reactive extractive distillation (SS-DCRED), were mainly explored via the thermodynamic and kinetic analysis. Subsequently, the multi-objective particle swarm optimization (MOPSO) algorithm was employed to optimize the process based on three objectives namely the total annual cost (TAC), CO2 emissions, and process route index (PRI). Finally, an efficient MCDM method combining CRITIC and TOPSIS was employed to rank the Pareto front solutions of the corresponding process design. Based on the comparison results, the optimal TCED process exhibits the lowest PRI with a decrease of 50.61% and 55.06% compared to that of the SS-DCRED and the DCRED, respectively. It also shows the best performance simultaneously considering economic, environmental, and safety criteria. Of note, the SS-DCRED separation process exhibited the lowest TAC, with a decrease of 60.67% and 11.45% compared to that of the TCED and the DCRED, respectively.

Troubleshooting the defect in the sampling line of the side stream capnograph.

Troubleshooting the defect in the sampling line of the side stream capnograph.

Growth and metabolism of halophilic Candida versatilis and Tetragenococcus halophilus in simultaneous and sequential fermentation of salted soy whey

This study investigated various strategies: mono-, simultaneous and sequential fermentation of halophilic Candida versatilis and Tetragenococcus halophilus to valorize salted whey, a side stream of salted tofu (pressed beancurd) production, with an ultimate goal of creating a soy sauce-like condiment. Growth, glucose, organic acids were monitored throughout fermentation, while free amino acids and volatile compounds were analyzed on the final days. In monoculture fermentation, both C. versatilis and T. halophilus thrived in salted soy whey. However, in co-culture fermentation, an antagonistic relationship was observed, wherein C. versatilis growth was slightly suppressed and T. halophilus was significantly inhibited. In C. versatilis-involved fermentations, no significant (p > 0.05) differences in key volatile and non-volatile chemical components were found among various fermentation modes. Key soy sauce-like volatile compounds, such as 4-ethylguaiacol and 4-ethylphenol, were detected in all C. versatilis-fermented salted soy whey, while T. halophilus primarily functioned as a lactic and acetic acids producer. This study highlights the potential of mixed culture fermentation involving soy sauce yeast and lactic acid bacteria for eventually developing a soy sauce-like condiment from salted soy whey, with C. versatilis playing a crucial role in flavour development. The findings suggest that fermenting of a single culture of C. versatilis in lactic acid-adjusted salted soy whey could be a viable and efficient choice for future production of soy sauce-like condiment.

Is Pulsed Electric Field (PEF) a Useful Tool for the Valorization of Solid and Liquid Sea Bass Side Streams?: Evaluation of Nutrients and Contaminants

AbstractIn this study, fresh sea bass’s (Dicentrarchus labrax) heads, skin, viscera, and muscle were evaluated for their potential valorization as a source of nutrients and bioactive compounds. For this purpose, a pulsed electric field (PEF) treatment (1.0 kV/cm field strength and 220.5 kJ/kg specific energy for head, 3.0 kV/cm and 299.4 kJ/kg for skin, 3.0 kV/cm and 123.7 kJ/kg for viscera and muscle) was used. Subsequently, extraction processes were carried out using either 100% water or 50% ethanol. Protein assessment (protein content and bioactive peptides’ identification), as well as ICP-MS analysis of minerals and heavy metals, was conducted on both the solid matrices and liquid extracts. The findings indicate that the choice of solvent (100% water or 50% ethanol) and PEF treatment significantly (p &lt; 0.05) affected protein recovery in the sea bass side streams liquid extracts, while a considerable protein amount was retained in the solid matrices. Furthermore, the ICP-MS analysis of minerals revealed that PEF treatment significantly (p &lt; 0.05) improved mineral recovery in the head and muscle liquid extracts. However, a considerable amount of minerals remained in the solid matrices. Lower contents of heavy metals were found in the liquid extracts compared to the solid matrices, being anyway the quantities of the five heavy metals analyzed within edible and safe limits. Additionally, the total antioxidant capacity (TAC) of sea bass side stream extracts was assessed to measure the potential antioxidant bioactive compounds in the liquid extracts. PEF treatments significantly (p &lt; 0.05) increased the TAC of the liquid extracts from sea bass viscera, as opposed to other side streams. Both 100% water and 50% ethanol were effective as extraction solvents, promoting the recovery of high-added-value compounds not only from the liquid extracts but also from solid matrices. Thus, PEF pre-treatment can be considered a valuable technique to enhance fish side stream valorization.

Extraction of water-soluble polysaccharides from lupin beans and their function of protein dispersion and stabilization under acidic conditions

In the current environment whereby new sources of proteins are extracted from plant material, it is also important to study the potential use of the resulting side streams. Although a number of studies have been conducted on various polysaccharides extracted from plant raw material, a polysaccharide fraction extracted from lupin bean is yet to be explored, in spite of the emerging interest in this crop as a source of food ingredients. In this work lupin soluble polysaccharide (LuPS) was obtained with a recovery as high as 46 % by extraction at pH 8, 120 °C, for 90 min. This fraction, named LuPS-8, was composed of a mostly linear pectic polysaccharide with a weight average molecular mass of 6608 kg/mol, and containing 71.0 % galactose, with minor amounts of arabinose (16.0 %), glucuronic acid 4.6 %, and galacturonic acid 4.1 %. When added to an acid milk dispersion, LuPS-8 improved its dispersibility, providing storage stability against sedimentation over a wider pH range than a HM-pectin reference, between 3.6–4.4. This research demonstrated the potential for upcycling of a side stream of lupin protein production, by the creation of value-added novel functional polysaccharide.

A vapor phase side stream intensified extractive distillation process for separation of azeotropic mixture 2, 2, 2-trifluoroethanol and water

2,2,2-Trifluoroethanol (TFE) is an important organic fluoride with various commercial applications. During the production of TFE through hydrolysis, an azeotrope of TFE and water can form, making it challenging to separate using conventional distillation. This study proposes a novel approach employing vapor phase side stream intensified extractive distillation separation (VSED) with glycerol serving as an entrainer to address this challenge. Additionally, a dividing wall column process (DWC) is established. The total annual cost (TAC), CO2 emissions and total energy cost (TEC) of the proposed separation processes are calculated and compared. The results indicate that VSED process can recover TFE with a purity of 0.9995 (mole fraction). VSED exhibits a TAC reduction of 34.2 % and a CO2 emissions reduction of 33.9 % compared to the CED process. In addition, a dual-composition control strategy is proposed for the VSED process. The results show that control strategy can effectively cope with the feed flow perturbation of ±20 % and the feed composition perturbation of ±5 %.

In situ fortification of protein-enriched brewer's spent grain with vitamin B12 by fermentation with Priestia megaterium and Propionibacteriumfreudenreichii

Meat is an important protein source in the human diet; however, the consumption of animal proteins needs to be reduced. Plant-based foods naturally lack cobalamin, vitamin B12 (VitB12), an essential vitamin in the human diet. Brewer's spent grain (BSG) is a side stream available in large volumes that was chosen as a substrate for food-grade VitB12-producing microorganisms.VitB12-producing microorganisms were identified in the scientific literature and selected to study in situ production of VitB12 in a protein-enriched (53%) BSG. A first screening was performed using Propionibacterium freudenreichii and Priestia megaterium (formerly known as Bacillus megaterium) strains. Further optimisations were exploited to increase the BSG content further and resulted in levels of up to 21 μg VitB12/100 g in the BSG at lab scale. Finally, experiments were performed at 12 kg scale fermentation with a stabilized pH and resulted in 7.7 μg VitB12/100 g BSG, indicating the potential of in situ fortification of BSG with VitB12 by fermentation with P. freudenreichii. Overall, it was found that the VitB12-fortified BSG could serve as a relatively inexpensive plant-based source of VitB12-fortified protein for food and feed applications. This study shows that fermentation offers opportunities to fortify (protein-enriched) BSG or other BSG derivatives with VitB12.

Untapped Potential of Side Stream Products from the Industrial Processing of Fruits: The Biosorption of Anthocyanins on Raspberry Seeds.

Natural biosorbents from agricultural side stream products are being investigated due to their large surface area and capacity for various compounds. The aim of the present work was to investigate the raspberry seeds and their sorption potential in the recovery of natural pigments. The experiment included raspberry seed and a liquid by-phase rich in anthocyanins initially collected during the depulping of the raspberry seed material. Biosorption was monitored by LC-MS analysis of the anthocyanins and by the total anthocyanin content (TAC) before and after biosorption. Cyanidins predominated in the seed material, followed by pelargonidins and peonidins. The efficiency of biosorption was examined by comparing the percent of removal. The heterogeneous polymer structure of the biosorbent, which consists mainly of lignin, cellulose, and hemicellulose, was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy (RS). The FTIR spectra of raw and defatted seed indicated functional groups involved in biosorption and principal component analysis (PCA) performed on Raman spectra pointed to differences among biosorbents. The developed strategy for the valorization of raspberry seeds in the recovery of natural colorants was shown to be effective, with recoveries from 49 to 88 percent of total anthocyanins.

Towards a circular economy - Repurposing side streams from the potato processing industry by Chlorella vulgaris

Common wastewater treatment strategies in the food industry do not include efficient remediation strategies for nitrogen, phosphorous and organic carbon. Incorporating microalgae in water treatment plants is rising in popularity because of their high nutrient and trace element uptake driven by light. In this study, four different side streams from an Austrian potato processing company have been screened for their applicability of microalgal cultivation. The side streams were assessed for Chlorella vulgaris growth and their requirement of any additional pretreatment or media supplementation. One side stream specifically, called blanching water II, a stream generated by boiling the potatoes for ease of peeling, turned out very useful to cultivate Chlorella vulgaris and concomitantly remedy the wastewater. Compared to a state-of-the-art cultivation in BG11, cultivating Chlorella vulgaris in blanching water II led to a 45 % increase in specific growth rate of 1.29 day−1 and a 48% increase in biomass productivity to 294.6 mg/L/day, while all nitrogen and phosphate present in the side stream were metabolized. Overall, the results demonstrate that the water remediation process for blanching water II shows vast potential in regard to water purification and waste to value approaches.