Nickel Hyperaccumulator Biochar Sorbs Ni(II) from Water and Wastewater to Create an Enhanced Bio-ore.

Nickel (Ni) hyperaccumulators make up the largest proportion of hyperaccumulator plant species; however, very few biochar studies with hyperaccumulator feedstock have examined them. This research addresses two major hypotheses: (1) Biochar synthesized from the Ni hyperaccumulator Odontarrhena chalcidica grown on natural, metal-rich soil is an effective Ni sorbent due to the plant's ability to bioaccumulate soluble and exchangeable cations; and (2) such biochar can sorb high concentrations of Ni from complex solutions. We found that O. chalcidica grew on sandy, nutrient-poor soil from a Minnesota mining district but did not hyperaccumulate Ni. Biochar prepared from O. chalcidica biomass at a pyrolysis temperature of 900 °C sorbed up to 154 mg g-1 of Ni from solution, which is competitive with the highest-performing Ni sorbents in recent literature and the highest of any unmodified, plant-based biochar material reported in the literature. Precipitation, cation exchange, and adsorption mechanisms contributed to removal. Ni was effectively removed from acidic solutions with initial pH > 2 within 30 min. O. chalcidica biochar also removed Ni(II) from a simulated Ni electroplating rinsewater solution. Together, these results provide evidence for O. chalcidica biochar as an attractive material for simultaneously treating high-Ni wastewater and forming an enhanced Ni bio-ore.

Parallel expansion and divergence of an adhesin family in pathogenic yeasts.

Opportunistic yeast pathogens arose multiple times in the Saccharomycetes class, including the recently emerged, multidrug-resistant (MDR) Candida auris. We show that homologs of a known yeast adhesin family in Candida albicans, the Hyr/Iff-like (Hil) family, are enriched in distinct clades of Candida species as a result of multiple, independent expansions. Following gene duplication, the tandem repeat-rich region in these proteins diverged extremely rapidly and generated large variations in length and ß-aggregation potential, both of which are known to directly affect adhesion. The conserved N-terminal effector domain was predicted to adopt a ß-helical fold followed by an α-crystallin domain, making it structurally similar to a group of unrelated bacterial adhesins. Evolutionary analyses of the effector domain in C. auris revealed relaxed selective constraint combined with signatures of positive selection, suggesting functional diversification after gene duplication. Lastly, we found the Hil family genes to be enriched at chromosomal ends, which likely contributed to their expansion via ectopic recombination and break-induced replication. Combined, these results suggest that the expansion and diversification of adhesin families generate variation in adhesion and virulence within and between species and are a key step toward the emergence of fungal pathogens.

Nickel Hyperaccumulator Biochar as a Ni-Adsorbent and Enhanced Bio-ore.

Increasing nickel (Ni) demand may spur the need for creative Ni production methods. Agromining (farming for metals) uses plants that can accumulate high concentrations of metal in their biomass, called bio-ore, as a metal extraction strategy. Furthermore, biochar, produced by biomass pyrolysis under low-oxygen conditions, can be used to remove Ni from contaminated wastewaters. In this work we investigate whether biochar synthesized from the Ni-hyperaccumulating plant Odontarrhena chalcidica (synonymous Alyssum murale) can be used as a Ni-adsorbing biochar. We grew O. chalcidica on soils with varying Ni concentration, characterized the plants and resultant biochars synthesized at different pyrolysis temperatures, and analyzed Ni batch adsorption results to determine the adsorption capacity of O. chalcidica biochar. We found that Ni concentration in O. chalcidica increases with increasing soil Ni but reaches an accumulation limit around 23 g Ni kg-1 dry weight in dried leaf samples. Pyrolysis concentrated Ni in the biochar; higher pyrolysis temperatures led to higher biochar Ni concentrations (max. 87 g Ni kg-1) and surface areas (max. 103 m2/g). Finally, the O. chalcidica biochar adsorption results were comparable to high-performing Ni adsorbents in the literature. The adsorption process greatly increased the Ni concentration in some biochars, indicating that synthesizing biochar from O. chalcidica biomass and using it as a Ni adsorbent can produce a Ni-enhanced bio-ore with nickel content higher than all nickel-rich veins currently mined.