Rapid Bacterial Community Changes during Vermicomposting of Grape Marc Derived from Red Winemaking

Abstract

Previous studies dealing with changes in microbial communities during vermicomposting were mostly performed at lab-scale conditions and by using low-throughput techniques. Therefore, we sought to characterize the bacterial succession during the vermicomposting of grape marc over a period of 91 days in a pilot-scale vermireactor. Samples were taken at the initiation of vermicomposting, and days 14, 28, 42, and 91, representing both active and mature stages of vermicomposting. By using 16S rRNA high-throughput sequencing, significant changes in the bacterial community composition of grape marc were found after 14 days and throughout the process (p < 0.0001). There was also an increase in bacterial diversity, both taxonomic and phylogenetic, from day 14 until the end of the trial. We found the main core microbiome comprised of twelve bacterial taxa (~16.25% of the total sequences) known to be capable of nitrogen fixation and to confer plant-disease suppression. Accordingly, functional diversity included increases in specific genes related to nitrogen fixation and synthesis of plant hormones (salicylic acid) after 91 days. Together, the findings support the use of grape marc vermicompost for sustainable practices in the wine industry by disposing of this high-volume winery by-product and capturing its value to improve soil fertility.

Temporal Dynamics of Bacterial Communities in a Pilot-Scale Vermireactor Fed with Distilled Grape Marc

“…This phylum is considered a fast-growing copiotroph group, while oligotrophic groups such as Actinobacteria, Planctomycetes, Verrucomicrobia and Chloroflexi reached higher levels on day 14, and the four of them, except for Actinobacteria, remained unchanged for the duration of the trial with distilled grape marc (Figure 3). Similarly, a rapid increase in Actinobacteria was found by Kolbe et al [25] on day 7, while Gómez-Brandón et al [7] observed a significant reduction in its abundance on day 14. Oligotrophic and copiotrophic bacterial groups mainly differed with regard to their growth strategies under nutrient rich conditions and their efficiency in metabolizing carbon substrates, i.e., labile and recalcitrant compounds for copiotrophs and oligotrophs, respectively [44].…”

“…Co-composting of distilled grape marc with other organic materials like green waste has been shown as a more effective alternative improving not only the compost quality but also shortening the time required to achieve stabilization [14]. Vermicomposting has also been successfully used to dispose of and treat large quantities of raw grape marc [2][3][4][5][6][7]16,17]. On the one hand, it may provide a means to neutralize the pH of this winery byproduct, as previously shown by Domínguez et al [2].…”

“…Grape marc, the major solid byproduct of the winemaking industry, has been used as an additive in animal feeding [1], and as a soil conditioner owing to its high level of organic matter and macronutrients [2][3][4][5][6][7]. This winery byproduct is also sent to distilleries, to recover ethanol for its further use in the elaboration of alcoholic beverages [8,9], and to cosmetic and pharmaceutical industries [6].…”

“…As microbial succession progresses, copiotrophic groups will be replaced by oligotrophic bacteria with a higher substrate utilization efficiency and the ability to metabolize the remaining recalcitrant substrates in the casts during the maturation stage [24]. By using sequencing-based microbiome analyses it has enabled us to enhance the throughput, and phylogenetically group and name a larger number of bacterial taxa in the vermicompost microbiome, as recently described for raw grape marc-derived vermicomposts of the cultivars Albariño [25] and Mencía [7]. Moreover, the application of high-throughput sequencing approaches has also facilitated the identification of bacterial taxa that drive keystone functions that may explain the beneficial effects of vermicomposts when applied to the soil and plants [25,26].…”

Bacterial community composition of vermicompost-treated tomato rhizospheres

“…Traditional work centered around cultured strains, mycorrhizae, and non-sequence-based methods of assessing microbial community structure [4]. More recently, sequencing-dependent analysis have become available that investigate changes in the microbiome during composting [22] and pathogen-vermicompost interactions [23]. Here, we investigate the impact of VC-extract treatments on bacterial microbiome assembly in each peat-and soil-grown tomato rhizospheres.…”