Evaluation of the enhanced resistance of Ogataea (Hansenula) polymorpha to benzalkonium chloride as a resource for bioremediation technologies

Elimination of inhibitory effects of dodecyl dimethyl benzyl ammonium chloride on microalgae in wastewater by cocultivation with a newly screened microbial consortium

As one of the most commonly used biocidal cationic surfactants, benzalkonium chlorides (BACs) have been an increasing concern as emerging contaminants. Wastewater has been claimed the main point for BACs to enter into the environment, but to date, it is still largely unknown how the BACs affect the microbes (especially microalgae) in the practical wastewater and how to cost-effectively remove them. In this study, the inhibitory effects of a typical BACs, dodecyl dimethyl benzyl ammonium chloride (DDBAC), on a green microalga Chlorella sp. in oxidation pond wastewater were investigated. The results showed that though a hermetic effect at the first 2 days was observed with the DDBAC at low concentration (<6 mg/L), the algal growth and photosynthesis were significantly inhibited by the DDBAC at all the tested concentrations (3 to 48 mg/L). Fortunately, a new microbial consortium (MC) capable of degrading DDBAC was screened through a gradient domestication method. The MC mainly composed of Wickerhamomyces sp., Purpureocillium sp., and Achromobacter sp., and its maximum removal efficiency and removal rate of DDBAC (48 mg/L) respectively reached 98.1 % and 46.32 mg/L/d. Interestingly, a microbial-microalgal system (MMS) was constructed using the MC and Chlorella sp., and a synergetic effect between the two kinds of microorganisms was proposed: microalga provided oxygen and extracellular polysaccharides as co-metabolic substrates to help the MC to degrade DDBAC, while the MC helped to eliminate the DDBAC-induced inhibition on the alga. Further, by observing the seven kinds of degradation products (mainly including CH5O3P, C6H5CH2-, and C8H11N), two possible chemical pathways of the DDBAC degradation were proposed. In addition, the metagenomic sequencing results showed that the main functional genes of the MMS included antibiotic-resistant genes, ABC transporter genes, quorum sensing genes, two-component regulatory system genes, etc. This study provided some theoretical and application findings for the cost-effective pollution prevention of BACs in wastewater.

Anthropogenic antimicrobial micropollutants and their implications for agriculture

Antibiotics and disinfectants have saved millions of human lives and cured uncountable animal diseases, but their activity is not limited to the site of application. Downstream, these chemicals become micropollutants, contaminating water at trace levels, resulting in adverse impacts on soil microbial communities and threatening crop health and productivity in agricultural settings and perpetuating the spread of antimicrobial resistance. Especially as resource scarcity drives increased reuse of water and other waste streams, considerable attention is needed to characterize the fate of antibiotics and disinfectants and to prevent or mitigate environmental and public health impacts. In this review, we hope to provide an overview of why increasing concentrations of micropollutants such as antibiotics are concerning in the environment, how they can pose health risks for humans, and how they can be countered using bioremediation strategies.

New concept for conversion of lignocellulose to ethanol and furfural

Studies on the chemical mechanisms of furfural formation showed the possibility to apply a new differential catalysis of hemicellulose - its depolymerisation and pentose dehydration to furfural. This change led to the increase in furfural yield and essential decrease of cellulose destruction. The lignocellulose residue that remains after the production of furfural may be subjected to enzymatic hydrolysis to glucose and the subsequent fermentation to ethanol. The remaining lignin appeared to be suitable for the production of additional various value-added products including medicinal mushrooms and laccase-containing enzyme complexes. Based on these developments, an innovative concept is proposed for the waste-free use of lignocellulose to obtain various valuable products. KEY POINTS: • New chemical mechanism of furfural production. • New lignocellulose pretreatment does not damage cellulose and lignin. • Lignocellulose may be processed using waste-free technology.