ABSTRACT
Methane from enteric fermentation is the gas with the greatest environmental impact emitted by ruminants. Lovastatin (Lv) addition to feedstocks could be a strategy to mitigate rumen methane emissions via decreasing the population of methanogenic archaea (MA). Thus, this paper provides the first overview of the effects of Lv supplementation, focusing on the inhibition of methane production, rumen microbiota, and ruminal fermentation. Results indicated that Lv treatment had a strong anti-methanogenic effect on pure strains of MA. However, there are uncertainties from in vitro rumen fermentation trials with complex substrates and rumen inoculum.Solid-state fermentation (SSF) has emerged as a cost-effective option to produce Lv. In this way, SSF of agricultural residues as an Lv-carrier supplement in sheep and goats demonstrated a consistent decrease in ruminal methane emissions. The experimental evidence for in vitro conditions showed that Lv did not affect the volatile fatty acids (VFA). However, in vivo experiments demonstrated that the production of VFA was decreased. Lv did not negatively affect the digestibility of dry matter during in vitro and in vivo methods, and there is even evidence that it can induce an increase in digestibility. Regarding the rumen microbiota, populations of MA were reduced, and no differences were detected in alpha and beta diversity associated with Lv treatment. However, some changes in the relative abundance of the microbiota were induced. Further studies are recommended on: (i) Lv biodegradation products and stability, as well as its adsorption onto the solid matter in the rumen, to gain more insight on the "available" or effective Lv concentration; and (ii) to determine whether the effect of Lv on ruminal fermentation also depends on the feed composition and different ruminants.
ABSTRACT
Mexican distilleries produce near eight million liters of mezcal per year, and generate about 90 million liters of mezcal vinasses (MV). This acidic liquid waste is very aggressive to the environment because of its high content of toxic and recalcitrant organic matter. As a result, treatment is necessary before discharge to water bodies. It is interesting, yet disturbing; verify that there is a significant gap on the treatment of MV. However, there is an abundant body of research on treatment of other recalcitrant toxic effluents that bear some similarity to MV, for example, wine vinasse, vinasses from the sugar industry, olive oil, and industrial pulp and paper wastewaters. The objective of this review is to critically organize the treatment alternatives of MV, assess their relative advantages and disadvantages, and finally detect the trends for future research and development. Experience with treatment of this set of residuals, indicates the following trends: (i) anaerobic digestion, complemented by oxidative chemical treatments (e.g. ozonation) are usually placed as pretreatments, (ii) aerobic treatment alone and combined with ozone which have been directed to remove phenolic compounds and color have been successfully applied, (iii) physico-chemical treatments such as Fenton, electro-oxidation, oxidants and so on., which are now mostly at lab scale stage, have demonstrated a significant removal of recalcitrant organic compounds, (iv) fungal pretreatment with chemical treatment followed by oxidative (O(3)) or anaerobic digestion, this combination seems to give attractive results, (v) vinasses can be co-composted with solid organic wastes, particularly with those from agricultural activities and agro-industies; in addition to soil amenders with fertilizing value to improve soil quality in typical arid lands where agave is cultivated, it seems to be a low cost technology very well suited for rural regions in underdeveloped countries where more sophisticated technologies are difficult to adopt, due to high costs and requirements of skilled personnel.
