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

Abstract

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.

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

“…Furthermore, the addition of PA lowered the abundance of Firmicutes and increased that of Proteobacteria . These changes are different from what we observed in our previous experiments using stylo and rice straw as silage materials ( 16 ). This might be because of different microbial communities in different silages.…”

“…In our study, PA decreased ( P < 0.05) ammonia-N content ( Table 2 ), which was in accord with the decline of coliform bacteria count. Similar results were found in stylo and rice straw silage in our previous study ( 16 ). The reduction of nonprotein-N content was also consistent with the decline of protease activities in PA-treated silage ( Table 3 ).…”

“…The addition of PA further reduced these pathways, which could have resulted from the direct acidification inhibiting the microbial activities. Our previous study found that PA reduced these pathways in stylo silage using 16S rRNA gene-predicted function ( 16 ).…”

“…Alfalfa was harvested at flowering stage in an experimental field of South China Agricultural University (Guangzhou, China) without application of chemical fertilizers and insecticides. The materials were immediately chopped (about 1-cm lengths), homogenized, and then treated with 1% PA and 2% PA on a fresh weight basis according to our previous study ( 16 ). Pyroligneous acid, kindly provided by Xiwei Xu (South China Agricultural University), was obtained using the method described by Xu et al ( 46 ) and then filtered using cellulose acetate membrane (0.45 μm).…”

“…Previous studies proved that PA had strong antibacterial activity on Escherichia , Salmonella , and Pseudomonas from animals ( 14 , 15 ). Our previous study found that PA could improve fermentation quality and change bacterial community of rice straw and stylo silages ( 16 ). Moreover, Zheng et al ( 6 , 13 ) reported that the application of PA significantly reduced the absolute abundance of ARGs to more than 80% in the soil.…”