Toxicity and Behavior-Altering Effects of Three Nanomaterials on Red Imported Fire Ants and Their Effectiveness in Combination with Indoxacarb.

The red imported fire ant (Solenopsis invicta Buren) is one of the 100 worst invasive alien species in the world. At present, the control of red imported fire ants is still mainly based on chemical control, and the most commonly used is indoxacarb bait. In this study, the contact and feeding toxicity of 16 kinds of nanomaterials to workers, larvae, and reproductive ants were evaluated after 24 h, 48 h, and 72 h. The results showed that the mortality of diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes among workers reached 98.67%, 97.33%, and 68%, respectively, after contact treatment of 72 h. The mortality of both larval and reproductive ants was less than 20% after 72 h of treatment. All mortality rates in the fed treatment group were below 20% after 72 h. Subsequently, we evaluated the digging, corpse-removal, and foraging behaviors of workers after feeding with diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes for 24 h, which yielded inhibitory effects on the behavior of red imported fire ants. The most effective was diatomite, which dramatically decreased the number of workers that dug, extended the time needed for worker ant corpse removal and foraging activities, decreased the number of workers that foraged, and decreased the weight of the food carried by the workers. In addition, we also evaluated the contact and feeding toxicity of these three nanomaterials in combination with indoxacarb on red imported fire ants. According to contact toxicity, after 12 h of contact treatment, the death rate among the red imported fire ants exposed to the three materials combined with indoxacarb reached more than 97%. After 72 h of exposure treatment, the mortality rate of larvae was more than 73% when the nanomaterial content was above 1% and 83% when the diatomite content was 0.5%, which was significantly higher than the 50% recorded in the indoxacarb control group. After 72 h of feeding treatment, the mortality of diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes combined with indoxacarb reached 92%, 87%, and 98%, respectively. The death rates of the three kinds of composite ants reached 97%, 67%, and 87%, respectively. The three kinds of composite food had significant inhibitory effects on the behavior of workers, and the trend was largely consistent with the effect of nanomaterials alone. This study provides technical support for the application of nanomaterials in red imported fire ant control.

Achieving efficient and rapid high-solids enzymatic hydrolysis for producing high titer ethanol with the assistance of di-rhamnolipids.

High-solids enzymatic hydrolysis is the premise of obtaining high concentration ethanol by fermentation. In this study, corn stover was first pretreated with formic acid under mild conditions, and more than 70 % of xylan and lignin were removed within the first hour. 173.0 g/L glucose was achieved from total 30 % solid of the pretreated corn stover via fed-batch mode. Moreover, the glucose concentration rose to 194.5 g/L and the hydrolysis time was significantly reduced by 42.9 % with the addition of di-rhamnolipid. On this basis, 89.1 g/L ethanol was obtained by fermentation, and the presence of di-rhamnolipid had no negative effect on fermentation. The effective conversion of corn stover to high titer ethanol provides support for the conversion of stover to ethanol in industrial production.

Addressing two major limitations in high-solids enzymatic hydrolysis by an ordered polyethylene glycol pre-incubated strategy: Rheological properties and lignin adsorption for enzyme.

High-solids enzymatic hydrolysis for biomass has currently received considerable interest. However, the solid effect during the process limits its economic feasibility. This work presented an ordered polyethylene glycol (PEG) pre-incubated strategy for enhancing the auxiliary effect of PEG in a high-solids enzymatic hydrolysis system. The substrate and enzyme were separately pre-incubated with PEG in this strategy. The ordered PEG pre-incubated strategies yielded a maximum glucose concentration of 166.6 g/L from 32 % (w/v) pretreated corncob with an enzymatic yield of 94.1 % by 72 h hydrolysis. Using this method, PEG not only lessened the lignin adsorption to cellulase but also altered particle rheological characteristics in the high-solids enzymatic hydrolysis system as a viscosity modifier. This study offered a new insight into the mechanism behind the PEG synergistic effect and would make it possible to achieve efficient high-solids loading hydrolysis in the commercial manufacture of cellulosic ethanol.

Fumigant toxicity and behavioral alterations of six plant essential oils against the red fire ant (Solenopsis invicta Buren).

The red imported fire ant (RIFA), Solenopsis invicta Buren (Hymenoptera: Formicidae), is an invasive species that is considered to be among the 100 most dangerous species to human health and the environment. RIFA is currently controlled primarily by chemical insecticides. However, human health concerns and environmental problems require environment friendly, green insect pest control technology. In this study, the HS-SPME-GC/MS method was used to determine the volatile components of six essential oils, namely Illicium verum Burm, Blumea balsamifera (L.) DC., Citrus limon Burm, Acorus tatarinowii Schott, Mosla chinensis Maxim, and Cinnamomum cassia Presl, as well as their fumigation activity against RIFA. D-Limonene was identified as a core volatile in all six essential oils. The effects of volatile substances from essential oils on the fumigation activity and behavior of RIFA workers were studied by closed fumigation method. Except for C. limon essential oil, all other five plant essential oils exhibit excellent fumigation activity under the treatment of a concentration at 10 µL/ cm3 within 24 h. All plant essential oils are capable of causing the death of all red fire ants, while C. limon essential oil exhibited the lowest fumigation activity at 63.25%. Significant reductions in RIFA aggregation, aggressiveness, and gripping abilities were observed with all plant essential oils, and antenna sensilla appeared to bend or break. Moreover, after treating red ant fire ants with essential oil for 24 h, three protective enzyme activities were assessed. All six plant essential oils were shown to have enhanced enzyme activities for superoxide dismutase (SOD), glutathione S-transferase (GST), and catalase (CAT). It has been shown that plant essential oils have the capability of reducing the viability of red fire ants via receptor and behavioral factors, ultimately causing them to die off. As a conclusion, plant oils were demonstrated to be negatively affecting RIFA and providing a green and environmentally sustainable control method in this study.

In-depth investigation of formic acid pretreatment for various biomasses: Chemical properties, structural features, and enzymatic hydrolysis.

Formic acid pretreatment is a promising approach for fractionating biomass, and it has the advantages of efficient recycling and removal of hemicellulose and lignin. Biomass is one of the most plentiful resources on earth, yet its chemical structure differs significantly between woody and herbaceous biomass. The influence of formic acid pretreatment on the fractionation of woody and herbaceous biomasses, as well as changes in physical-chemical properties, was investigated in this study. The results indicated that formic acid is universal in the biorefinery of different biomass, however, herbaceous biomass had greater xylan and lignin removal than woody biomass (especially softwood). Formic acid pretreatment not only considerably improved the enzymatic efficiency of herbaceous biomass, but also had a good effect on the enzymatic efficiency of poplar. This study also found that the correlation between residual xylan content and enzymatic efficiency after pretreatment was much higher than that of lignin content.