Despite all the applications of nanotechnology, limited data are available on their environmental and health risks. Many nanomaterials have been developed; however, their safety evaluation is not performed at the same speed. Toxicity can occur at different trophic levels (microorganisms, invertebrates, and vertebrates), and because of that, alternative/complementary models have been successfully employed. This mini-review aims to report some studies that have successfully used different alternative models to assess nanotoxicology and to stimulate their use by other groups of this important field. This will provide more information about nanomaterials and also to evoke studies to improve formulations.

Lignin is one of the most abundant natural materials with many important roles, especially in providing structural resilience of plants. It is formed through the radical polymerization of aromatic monomers and shows structural and compositional differences depending on sources, biosynthesis and processes used for its extraction. Herein, we present extraction of lignin from the Citrus sinensis (sweet orange) bagasse using full sequential extraction in a yield of 0.34% and report on the soda lignin nuclear magnetic resonance (NMR) properties (¹H NMR and 2D NMR). The soda lignin was then applied in the sustainable synthesis of silver nanoparticles (AgNPs). The obtained silver nanoparticles showed unimodal distribution of sizes, spherical morphology, average diameters of 19.1 ± 4.7 nm and negative zeta potentials of − 28.5 ± 3.2 mV. The AgNPs were also found to be stable over several months.

The increase in the production of carbon nanotubes (CNT) arises potential scenarios of exposure to these nanomaterials for several organisms including aquatic species. Experiments were conducted to determine the toxicity of single-walled (SWCNT) and multi-walled (MWCNT) carbon nanotubes to the fish Danio rerio (Cyprinidae) exposed to these CNT via diet (500 mg/kg) during 28 days. Induction of oxidative stress by CNT was evaluated through protein carbonyl groups (immunohistochemistry). Higher levels of carbonyl groups were registered in several organs (liver, brain, pancreas and muscle) of fish exposed to SWCNT and MWCNT. Overall, data indicate that CNT administered through diet can in fact induce toxicological responses in aquatic organisms as fish. The measurement of irreversible protein oxidative damage through immunohistochemistry seems to be a valuable tool for nanotoxicology.

Frequent exposure of microbes to hazardous metalloids/heavy metals in contaminated environment results in the development of heavy metal(loid)-resistance properties. The study attempted to assess the profile of elevated arsenic (As), cadmium (Cd) and mercury (Hg)—resistant bacterial community structures of sludge (S1, India), sludge and sediment (S2 and S3, Japan) and sediment (S4, Vietnam) samples by metagenomic-DNA fingerprinting using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR–DGGE) for monitoring and bioremediation of hazardous metal(loid) contamination in environment. The results revealed that As-resistant bacteria were dominant compared to Cd- and Hg-resistant bacteria with higher species diversity (Lysinibacillus sp., Uncultured soil bacterium clone, Staphylococcus sciuri, Bacillus fastidiosus, Bacillus niacini, Clostridium sp. and Bacillus sp.) in S1 and S4 than that of S2 and S3 samples. The occurrence of dominant As-resistant bacteria may indicate arsenic contamination in the investigated coastal habitats of India, Japan and Vietnam. The As-, Cd- and Hg-resistant bacteria/bacterial consortiums showed appreciable uptake ability of respective metal(loid) (0.042–0.125 mg As/l, 0.696–0.726 mg Cd/l and 0.34–0.412 mg Hg/l). Therefore, it might be concluded that the profiling of metalloids/heavy metal-resistant bacterial community structure by metagenomic-DNA fingerprinting using PCR–DGGE could be used to explore high metal(loid)-resistant bacteria for applying in metal(loid) bioremediation and as an indicator for monitoring hazardous metal(loid) contamination in environment.

Escherichia coli (E. coli) populations could become tolerant to extreme environmental temperatures to become resident in soil and surface water habitats creating public health problems. The objective of this study was to understand the interaction between dynamics of E. coli genetic diversity, physiology, and vegetative filter strips (VFS) in overland flows and soil habitats. Pulse-field gel electrophoresis was used to establish the genetic diversity of the isolates (n = 4). Genotypic analysis showed that the runoff isolates do not form a single genetic strain, but that multiple genotype strains were capable of surviving and proliferating in these habitats. High overall unique genotypic diversity was observed in VFS II (38.5%) as compared to VFS III (9.5%) and VFS I (1.5%). Approximately 8.5% E. coli genotypes observed in the surface water and 5.5% observed in soil habitat were shared between different sampling sites, suggesting diffuse sources of E. coli in these habitats. Approximately 32.5% genotypic overlap and a limited sharing (72.5%) between soil and surface water habitats were observed. These findings inferred that certain E. coli strains might have the ability to colonize and adapt to soil and runoff surface water habitats through production of biofilms. Thus, these results confirm that biofilm formation confers competitive advantage to the E. coli environmental isolates including hardiness, versatility, higher resistance to ecological and physical impacts and higher resource availability.

Lignocellulosic biomass (LB) despite its huge potential as a renewable bioenergy resource faces bottlenecks due to its recalcitrance and lack of appropriate pretreatment approaches. The current study evaluates the combinatorial application of alkali and acid pretreatment of pine needle biomass (PNB), for achieving high sugar release upon enzymatic saccharification. Pine needle accumulation poses a big threat to the forest soil fertility and overall ecosystem and environment. However, pine needle waste can be valorized after appropriate pretreatment and enzymatic saccharification for production of renewable energy, i.e. biofuel–ethanol. In combinatorial pretreatment strategy, first PNB was subjected to ammonium carbonate pretreatment, and parameters like ammonium carbonate concentration, incubation time and pretreatment temperature were optimized using design of experiment (DoE) approach. The relative influence of parameters on efficacy of pretreatment was established individually and in interactive terms. Based on DoE, sugar yield of 7.56 mg/g of PNB was obtained. Furthermore, DoE-based pretreated PNB was subjected to sulphuric acid pretreatment, followed by enzymatic saccharification. The sugar released during various steps was pooled (8.19 g/100 g), concentrated and subjected to ethanol fermentation with dual yeast cultures using Saccharomyces cerevisiae and Pichia stipitis. An ethanol yield of 8.8%, v/v (6.94% w/v), was obtained. This represents the process efficiency of 19.34% for bioethanol production from PNB.