Cellulose Nanocrystals and Lignin Nanoparticles Extraction from Lemna minor L.: Acid Hydrolysis of Bleached and Ionic Liquid-Treated Biomass

Using biomass to develop and obtain environmentally friendly and industrially applicable biomaterials is increasingly attracting global interest. Herein, cellulose nanocrystals (CNCs) and lignin nanoparticles (LNPs) were extracted from Lemna minor L., a freshwater free-floating aquatic species commonly called duckweed. To obtain CNCs and LNPs, two different procedures and biomass treatment processes based on bleaching or on the use of an ionic liquid composed of triethylammonium and sulfuric acid ([TEA][HSO4]), followed by acid hydrolysis, were carried out. Then, the effects of these treatments in terms of the thermal, morphological, and chemical properties of the CNCs and LNPs were assessed. The resulting nanostructured materials were characterized by using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, thermo-gravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the two methodologies applied resulted in both CNCs and LNPs. However, the bleaching-based treatment produced CNCs with a rod-like shape, length of 100-300 nm and width in the range of 10-30 nm, and higher purity than those obtained with ILs that were spherical in shape. In contrast, regarding lignin, IL made it possible to obtain spherical nanoparticles, as in the case of the other treatment, but they were characterized by higher purity and thermal stability. In conclusion, this research highlights the possibility of obtaining nanostructured biopolymers from an invasive aquatic species that is largely available in nature and how it is possible, by modifying experimental procedures, to obtain nanomaterials with different morphological, purity, and thermal resistance characteristics.

Taro raphide-associated proteins: Allergens and crystal growth

Calcium oxalate raphide crystals are found in bundles in intravacuolar membrane chambers of specialized idioblasts cells of most plant families. Aroid raphides are proposed to cause acridity in crops such as taro (Colocasia esculenta (L.) Schott). Acridity is irritation that causes itchiness and pain when raw/insufficiently cooked tissues are eaten. Since raphides do not always cause acridity and since acridity can be inactivated by cooking and/or protease treatment, it is possible that a toxin or allergen-like compound is associated with the crystals. Using two-dimensional (2D) gel electrophoresis and mass spectrometry (MS) peptide sequencing of selected peptides from purified raphides and taro apex transcriptome sequencing, we showed the presence on the raphides of peptides normally associated with mitochrondria (ATP synthase), chloroplasts (chaperonin ~60 kDa), cytoplasm (actin, profilin), and vacuole (V-type ATPase) that indicates a multistage biocrystallation process ending with possible invagination of the tonoplast and addition of mucilage that may be derived from the Golgi. Actin might play a crucial role in the generation of the needle-like raphides. One of the five raphide profilins genes was highly expressed in the apex and had a 17-amino acid insert that significantly increased that profilin's antigenic epitope peak. A second profilin had a 2-amino acid insert and also had a greater B-cell epitope prediction. Taro profilins showed 83% to 92% similarity to known characterized profilins. Further, commercial allergen test strips for hazelnuts, where profilin is a secondary allergen, have potential for screening in a taro germplasm to reduce acridity and during food processing to avoid overcooking.

Microscopic structure of the polymer-induced liquid precursor for calcium carbonate

Many biomineral crystals form complex non-equilibrium shapes, often via transient amorphous precursors. Also in vitro crystals can be grown with non-equilibrium morphologies, such as thin films or nanorods. In many cases this involves charged polymeric additives that form a polymer-induced liquid precursor (PILP). Here, we investigate the CaCO3 based PILP process with a variety of techniques including cryoTEM and NMR. The initial products are 30-50 nm amorphous calcium carbonate (ACC) nanoparticles with ~2 nm nanoparticulate texture. We show the polymers strongly interact with ACC in the early stages, and become excluded during crystallization, with no liquid-liquid phase separation detected during the process. Our results suggest that "PILP" is actually a polymer-driven assembly of ACC clusters, and that its liquid-like behavior at the macroscopic level is due to the small size and surface properties of the assemblies. We propose that a similar biopolymer-stabilized nanogranular phase may be active in biomineralization.