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

María Gómez-Brandón,Manuel Aira,Natielo Santana,Marcos Pérez-Losada,Jorge Domínguez

doi:10.3390/microorganisms8050642

Abstract

Vermicomposting has been found as a profitable approach to dispose of and treat large quantities of raw grape marc. However, less information is available with regard to its efficiency for treating distillery winery byproducts, even though distillation has been widely used as a way to economically valorize grape marc. As such, we sought to characterize the compositional and functional changes in bacterial communities during vermicomposting of distilled grape marc by using 16S rRNA high-throughput sequencing. Samples were collected at the initiation of vermicomposting and at days 14, 21, 28, 35 and 42. There were significant changes (p < 0.0001) in the bacterial community composition of distilled grape marc after 14 days of vermicomposting that were accompanied by twofold increases in bacterial richness and diversity from a taxonomic and phylogenetic perspective. This was followed by significant increases in functional diversity of the bacterial community, including metabolic capacity, lignin and cellulose metabolism, and salicylic acid synthesis. These findings indicate that the most striking compositional and functional bacterial community changes took place during the active phase of the process. They also pinpoint functional attributes that may be related to the potential beneficial effects of distilled grape marc vermicompost when applied on soil and plants.

Highlights

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]
In order to describe the bacterial changes during vermicomposting of distilled grape marc, we focused on a fragment of the 16S rRNA gene covering the V4 region, by using a dual-index sequencing strategy, as described by Kozich et al [28]
Microbial activity assessed as basal respiration significantly decreased from the beginning of the experiment until day 28, followed by no more noticeable changes until the end of the trial on day 42 (Figure 1). This points to the effectiveness of vermicomposting at biologically stabilizing the distilled grape marc, as shown by the lower and stable values of basal respiration from day 28 onwards (Figure 1). These results indicate that the contributions of earthworms to the process can be grouped into two stages, comprising the active phase of vermicomposting and the maturation phase

Summary

Introduction

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 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]. On the other hand, vermicomposting has been shown to effectively reduce organic biomass and generate high-quality fertilizer with beneficial effects on soil and plants [18,19]

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Discussion

Conclusion