Exogenous bamboo pyroligneous acid improves antioxidant capacity and primes defense responses of harvested apple fruit

Bamboo leaf extract treatment alleviates the surface browning of fresh-cut apple by regulating membrane lipid metabolism and antioxidant properties

BACKGROUND

The effect of bamboo leaf extract (BLE) on controlling the browning of fresh-cut apple stored at 4 °C was investigated. Browning index, H2 O2 content, O2 - production rate, malondialdehyde (MDA) contents, total phenolic content (TPC) and soluble quinone content (SQC), the activities of polyphenol oxidase (PPO), peroxidase (POD), lipoxygenase (LOX), superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), DPPH (2,2-diphenyl-2-picryl-hydrazyl) and ABTS [2,2-azinobis(3-ethylbenzothiazoline- 6-sulfonic acid)] radical scavenging activities, and the expression of genes related to browning were all investigated.

RESULTS

BLE effectively alleviated the surface browning of fresh-cut apple, accompanied by a reduction in SQC, LOX activity, H2 O2 , O2 - production rate and MDA accumulation. Furthermore, BLE treatment enhanced the TPC, enzymatic (SOD, CAT, APX and POD) and non-enzymatic antioxidant activities. Principal component analysis and Pearson correlation analysis found the browning inhibition by BLE is not through the reduction of phenolic substrates and PPO activity.

CONCLUSION

BLE controls the browning of fresh-cut apple by increasing the antioxidant capacity to scavenge ROS, which could alleviate oxidative damage and maintain the membrane integrity. © 2023 Society of Chemical Industry.

Inhibitory effects of hinokitiol on the development and pathogenicity of Colletotrichum gloeosporioides

Postharvest anthracnose of mango fruit caused by Colletotrichum gloeosporioides is a devastating fungal disease, which causes tremendous quality deterioration and economic losses. Hinokitiol, an environmentally friendly natural compound, is effective in controlling a variety of postharvest fungal diseases. However, there is still a lack of research on the inhibitory effect of hinokitiol on C. gloeosporioides and its possible modes of action. In the present study, the activity of hinokitiol against C. gloeosporioides and its potential mechanisms involved have been investigated. We found that hinokitiol treatment could effectively inhibit the virulence of C. gloeosporioides to harvested mango fruit. After treatment with 8 mg/L hinokitiol, the mycelial growth of C. gloeosporioides was completely inhibited. When the concentration of hinokitiol reached 9 mg/L, the spore germination rate of C. gloeosporioides decreased to 2.43% after 9 h of cultivation. The inhibitory effect is mainly due to the attenuation in cell viability, and impairment in plasma membrane followed by leakage of cytoplasmic contents such as nucleic acids, proteins, and soluble carbohydrates, which ultimately leads to the destruction of cell structure. Furthermore, hinokitiol suppressed the expression of pathogenicity-related genes, leading to reduced infection activity. Collectively, these results suggest that hinokitiol may be an excellent bio-fungicides for the management of mango anthracnose.

Effects of Pyroligneous Acid on Diversity and Dynamics of Antibiotic Resistance Genes in Alfalfa Silage

Antibiotic resistance genes (ARGs) are recognized as contaminants due to their potential risk for human and environment. The aim of the present study is to investigate the effects of pyroligneous acid (PA), a waste of biochar production, on fermentation characteristics, diversity, and dynamics of ARGs during ensiling of alfalfa using metagenomic analysis. The results indicated that PA decreased (P < 0.05) dry matter loss, pH value, gas production, coliform bacteria count, protease activity, and nonprotein-N, ammonia-N, and butyric acid contents and increased (P < 0.05) lactic acid content during ensiling. During fermentation, Bacteria, Firmicutes, and Lactobacillus were the most abundant at kingdom, phylum, and genus levels, respectively. Pyroligneous acid reduced the relative abundance of Bacteria and Firmicutes and increased that of Lactobacillus. The detected ARGs belonged to 36 drug classes, including mainly macrolides, tetracycline, lincosamides, and phenicol. These types of ARGs decreased during fermentation and were further reduced by PA. These types of ARGs were positively correlated (P < 0.05) with fermentation parameters like pH value and ammonia-N content and with bacterial communities. At the genus level, the top several drug classes, including macrolide, tetracycline, lincosamide, phenicol, oxazolidinone, streptogramin, pleuromutilin, and glycopeptide, were positively correlated with Staphylococcus, Streptococcus, Listeria, Bacillus, Klebsiella, Clostridium, and Enterobacter, the potential hosts of ARGs. Overall, ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community composition. Ensiling could be a feasible way to mitigate ARGs in forages. The addition of PA could not only improve fermentation quality but also reduce ARG pollution of alfalfa silage.

IMPORTANCE Antibiotic resistance genes (ARGs) are considered environmental pollutants posing a potential human health risk. Silage is an important and traditional feed, mainly for ruminants. ARGs in silages might influence the diversity and distribution of ARGs in animal intestinal and feces and then the manure and the manured soil. However, the diversity and dynamics of ARGs in silage during fermentation are still unknown. We ensiled alfalfa, one of the most widely used forages, with or without pyroligneous acid (PA), which was proved to have the ability to reduce ARGs in soils. The results showed that ARGs in alfalfa silage were abundant and were influenced by the fermentation parameters and microbial community. The majority of ARGs in alfalfa silage reduced during fermentation. The addition of PA could improve silage quality and reduce ARG pollution in alfalfa silage. This study can provide useful information for understanding and controlling ARG pollution in animal production.

Influence of Pyroligneous Acid on Fermentation Parameters, CO2 Production and Bacterial Communities of Rice Straw and Stylo Silage

Carbon dioxide (CO₂) is a primary greenhouse gas and the main cause of global warming. Respiration from plant cells and microorganisms enables CO₂ to be produced during ensiling, a method of moist forage preservation applied worldwide. However, limited information is available regarding CO₂ emissions and mitigation during ensiling. Pyroligneous acid, a by-product of plant biomass pyrolysis, has a strong antibacterial capacity. To investigate CO₂ production and the influence of pyroligneous acid, fresh stylo, and rice straw were ensiled with or without 1% or 2% pyroligneous acid. Dynamics of the fermentation characteristics, CO₂ production, and bacterial communities during ensiling were analyzed. Pyroligneous acid increased the lactic acid content and decreased the weight losses, pH, ammonia-N content, butyric acid content, and coliform bacterial numbers (all P < 0.05). It also increased the relative abundance of Lactobacillus and decreased the relative abundances of harmful bacteria such as Enterobacter and Lachnoclostridium. Adding pyrolytic acids reduced the gas production, especially of CO₂. It also increased the relative abundances of CO₂-producing bacterial genera and of genera with the potential for CO₂ fixation. In conclusion, adding pyroligneous acid improved the fermentation quality of the two silages. During ensiling, CO₂ production was correlated with bacterial community alterations. Using pyroligneous acid altered the bacterial community to reduce CO₂ production during ensiling. Given the large production and demand for silage worldwide, application of pyroligneous acid may be an effective method of mitigating global warming via CO₂ emissions.