DRY biorefineries: Multiscale modeling studies and innovative processing

Plant-based proteins from agro-industrial waste and by-products: Towards a more circular economy

There is a pressing need for affordable, abundant, and sustainable sources of proteins to address the rising nutrient demands of a growing global population. The food and agriculture sectors produce significant quantities of waste and by-products during the growing, harvesting, storing, transporting, and processing of raw materials. These waste and by-products can sometimes be converted into valuable protein-rich ingredients with excellent functional and nutritional attributes, thereby contributing to a more circular economy. This review critically assesses the potential for agro-industrial wastes and by-products to contribute to global protein requirements. Initially, we discuss the origins and molecular characteristics of plant proteins derived from agro-industrial waste and by-products. We then discuss the techno-functional attributes, extraction methods, and modification techniques that are applied to these plant proteins. Finally, challenges linked to the safety, allergenicity, anti-nutritional factors, digestibility, and sensory attributes of plant proteins derived from these sources are highlighted. The utilization of agro-industrial by-products and wastes as an economical, abundant, and sustainable protein source could contribute towards achieving the Sustainable Development Agenda's 2030 goal of a "zero hunger world", as well as mitigating fluctuations in food availability and prices, which have detrimental impacts on global food security and nutrition.

Dry fractionation process operations in the production of protein concentrates: A review

The market for plant proteins is expanding rapidly as the negative impacts of animal agriculture on the environment and resources become more evident. Plant proteins offer competitive advantages in production costs, energy requirements, and sustainability. Conventional plant-protein extraction is water and chemical-intensive, posing environmental concerns. Dry fractionation is an energy-efficient and environmentally friendly process for protein separation, preserving protein's native functionality. Cereals and pulses are excellent sources of plant proteins as they are widely grown worldwide. This paper provides a comprehensive review of the dry fractionation process utilized for different seeds to obtain protein-rich fractions with high purity and functionality. Pretreatments, such as dehulling and defatting, are known to enhance the protein separation efficiency. Factors, such as milling speed, mill classifier speed, feed rate, seed type, and hardness, were crucial for obtaining parent flour of desired particle size distribution during milling. The air classification or electrostatic separation settings are crucial in determining the quality of the separated protein. The cut point in air classification is targeted based on the starch granule size of the seed material. Optimization of these operations, applied to different pulses and seeds, led to higher yields of proteins with higher purity. Dual techniques, such as air classification and electrostatic separation, enhance protein purity. The yield of the protein concentrates can be increased by recycling the coarse fractions. Further research is necessary to improve the quality, purity, and yield of protein concentrates to enable more efficient use of plant proteins to meet global protein demands.

Maize Internode Autofluorescence at the Macroscopic Scale: Image Representation and Principal Component Analysis of a Series of Large Multispectral Images

A quantitative histology of maize stems is needed to study the role of tissue and of their chemical composition in plant development and in their end-use quality. In the present work, a new methodology is proposed to show and quantify the spatial variability of tissue composition in plant organs and to statistically compare different samples accounting for biological variability. Multispectral UV/visible autofluorescence imaging was used to acquire a macroscale image series based on the fluorescence of phenolic compounds in the cell wall. A series of 40 multispectral large images of a whole internode section taken from four maize inbred lines were compared. The series consisted of more than 1 billion pixels and 11 autofluorescence channels. Principal Component Analysis was adapted and named large PCA and score image montages at different scales were built. Large PCA score distributions were proposed as quantitative features to compare the inbred lines. Variations in the tissue fluorescence were clearly displayed in the score images. General intensity variations were identified. Rind vascular bundles were differentiated from other tissues due to their lignin fluorescence after visible excitation, while variations within the pith parenchyma were shown via UV fluorescence. They depended on the inbred line, as revealed by the first four large PCA score distributions. Autofluorescence macroscopy combined with an adapted analysis of a series of large images is promising for the investigation of the spatial heterogeneity of tissue composition between and within organ sections. The method is easy to implement and can be easily extended to other multi-hyperspectral imaging techniques. The score distributions enable a global comparison of the images and an analysis of the inbred lines' effect. The interpretation of the tissue autofluorescence needs to be further investigated by using complementary spatially resolved techniques.

A Circular Approach for the Valorization of Tomato By-Product in Biodegradable Injected Materials for Horticulture Sector

This study focuses on the use of tomato (Solanum lycopersicum L.) by-product biomass from industrial plants as reinforcement for designing a range of new degradable and biobased thermoplastic materials. As a novel technique, this fully circular approach enables a promising up-cycling of tomato wastes. After an in-depth morphological study of the degree of reinforcement through SEM and dynamic analysis, mechanical characterization was carried out. Our mechanical results demonstrate that this circular approach is of interest for composite applications. Despite their moderate aspect ratio values (between 1.5 and 2), the tomato by-product-reinforced materials can mechanically compete with existing formulations; PBS-Tomato fiber, for example, exhibits mechanical performance very close to that of PP-flax, especially regarding strength (+11%) and elongation at break (+6%). According to the matrix and particle morphology, a large range of products-biobased and/or degradable, depending on the targeted application-can be designed from tomato cultivation by-products.

Enzymatic degradation of maize shoots: monitoring of chemical and physical changes reveals different saccharification behaviors

BACKGROUND

The recalcitrance of lignocellulosics to enzymatic saccharification has been related to many factors, including the tissue and molecular heterogeneity of the plant particles. The role of tissue heterogeneity generally assessed from plant sections is not easy to study on a large scale. In the present work, dry fractionation of ground maize shoot was performed to obtain particle fractions enriched in a specific tissue. The degradation profiles of the fractions were compared considering physical changes in addition to chemical conversion.

RESULTS

Coarse, medium and fine fractions were produced using a dry process followed by an electrostatic separation. The physical and chemical characteristics of the fractions varied, suggesting enrichment in tissue from leaves, pith or rind. The fractions were subjected to enzymatic hydrolysis in a torus reactor designed for real-time monitoring of the number and size of the particles. Saccharification efficiency was monitored by analyzing the sugar release at different times. The lowest and highest saccharification yields were measured in the coarse and fine fractions, respectively, and these yields paralleled the reduction in the size and number of particles. The behavior of the positively- and negatively-charged particles of medium-size fractions was contrasted. Although the amount of sugar release was similar, the changes in particle size and number differed during enzymatic degradation. The reduction in the number of particles proceeded faster than that of particle size, suggesting that degradable particles were degraded to the point of disappearance with no significant erosion or fragmentation. Considering all fractions, the saccharification yield was positively correlated with the amount of water associated with [5-15 nm] pore size range at 67% moisture content while the reduction in the number of particles was inversely correlated with the amount of lignin.

CONCLUSION

Real-time monitoring of sugar release and changes in the number and size of the particles clearly evidenced different degradation patterns for fractions of maize shoot that could be related to tissue heterogeneity in the plant. The biorefinery process could benefit from the addition of a sorting stage to optimise the flow of biomass materials and take better advantage of the heterogeneity of the biomass.

Catalytic liquefaction of sewage sludge to small molecular weight chemicals

The catalytic hydrotreatment of sewage sludge, the wet solid byproducts from wastewater treatment plants, using supported Ir, Pt, Pd, Ru catalysts had been investigated with different solvent conditions. Reactions were carried out in a batch set-up at elevated temperatures (400 °C) using a hydrogen donor (formic acid (FA) in isopropanol (IPA) or hydrogen gas), with sewage sludge obtained from different sampling places. Sewage sludge conversions of up to 83.72% were achieved using Pt/C, whereas the performance for the others catalysts is different and solvent had a strong effect on the conversion rate and product constitution. The sewage sludge oils were characterised using a range of analytical techniques (GC, GC-MS, GCxGC, GPC) and were shown to consist of monomers, mainly alkanes and higher oligomers.

Comminution of Dry Lignocellulosic Biomass: Part II. Technologies, Improvement of Milling Performances, and Security Issues

Lignocellulosic feedstocks present a growing interest in many industrial processes as they are an ecological alternative to petroleum-based products. Generally, the size of plant raw materials needs to be reduced by milling step(s), to increase density, facilitate transport and storage, and to increase reactivity. However, this unit operation can prove to be important in term of investments, functioning costs, and energy consumption if the process is not fully adapted to the histological structure of the plant material, possibly challenging the profitability of the whole chain of the biomass conversion. In this paper, the different technologies that can be used for the milling of lignocellulosic biomass were reviewed and different avenues are suggested to improve the milling performances thanks to thermal pretreatments. Based on examples on wheat straw milling, the main points to take into consideration in the choice of a milling technologies have been highlighted in regards to the specifications of ground powder. A specific focus on the hazards associated to the milling and the manipulation of fine biomass particles is also realized at the end of the paper from the perspective of industrial applications.

Comminution of Dry Lignocellulosic Biomass, a Review: Part I. From Fundamental Mechanisms to Milling Behaviour

The comminution of lignocellulosic biomass is a key operation for many applications as bio-based materials, bio-energy or green chemistry. The grinder used can have a significant impact on the properties of the ground powders, of those of the end-products and on the energy consumption. Since several years, the milling of lignocellulosic biomass has been the subject of numerous studies most often focused on specific materials and/or applications but there is still a lack of generic knowledge about the relation between the histological structure of the raw materials, the milling technologies and the physical and chemical properties of the powders. This review aims to point out the main process parameters and plant raw material properties that influence the milling operation and their consequences on the properties of ground powders and on the energy consumption during the comminution.