Xanthan production on wastewaters from wine industry

Abstract

Wine industry generates large volumes of wastewaters resulting from numerous cleaning operations that occur during the different stages of winemaking. Disposal of these effluents in the environment causes huge problems due to their high organic and inorganic load and seasonal variability. The bioconversion of winery wastewaters in valuable product, such as xanthan, is an important alternative to overcome environmental problems. In this research, the possibility of xanthan production using Xanthomonas campestris on blended wastewaters from different stages of white and rose wine production with initial sugar content of 50 g/L was investigated. In addition to the media parameters (content of sugars, total and assimilable nitrogen, phosphorus, total dissolved salts and apparent viscosity), raw xanthan yield and degree of sugar conversion into product were determined in order to examine the success of xanthan biosynthesis. In applied experimental conditions, xanthan yield of 20.92 and 30.64 g/L and sugar conversion into product of 40.23 and 60.73% were achieved on wastewaters from white and rose wine production, respectively. The results of these experiments suggest that winery wastewaters, after additional optimization of the process in terms of the substrate composition and the cultivation conditions, may be a suitable raw material for industrial xanthan production.

Xanthan biosynthesis by Xanthomonas campestris ATCC 13951 on wastewaters from white grape processing

“…The sugars content, expressed as the sum of glucose and fructose, was determined in samples of cultivation medium and obtained results are shown in Figure 1b. Presented results indicate that sugars content considerably decreased during 96 h of cultivation, similar to the literature data (Rončević et al, 2017). During the first 24 h sugars has been mainly used for the growth of X. campestris cells (Figure 1a).…”

“…After 96 h of cultivation contents of total and assimilable nitrogen were 133.00 mg/L and 2.80 mg/L, while conversions rate were 48.65% and 95.65%, respectively. Despite the fact that assimilable nitrogen content was higher (about 30%) in winery wastewaters used in previous research (Rončević et al, 2017), a larger conversions of total and assimilable nitrogen were achieved in this experiment.…”

“…After that period these compounds was used for maintenance of energy activity of producing microorganism, but also for the xanthan biosynthesis, because the cells were in the stationary phase (Figure 1a) which is characterized by the highest production of this biopolymer. At the end of the bioprocess, residual sugars content in winery wastewater based medium was 3.55 g/L, thus achieving the sugars conversion of 82.98%, which is even more comparing to previously obtained value of this parameter (63.53%) (Rončević et al, 2017). Presented results suggest that in applied experimental conditions the large percentage of sugars compounds from winery wastewaters was utilized on biomass growth and xanthan biosynthesis making this bioprocess cost-effective.…”

“…In previous studies it has been confirmed that xanthan can be produced by cultivation of Xanthomonas campestris on wastewaters from different stages of rose and white wine production, as well as their mixtures (Rončević et al, 2017). Xanthan is extracellular heteropolysaccharide and commercially most important biopolymer.…”

“…It is reported that glucose concentrations of 10-50 g/L are suitable for xanthan production, while the yield of desired product is decreased at higher glucose content (Papagianni et al, 2001). In addition, the results of previous study indicate that media based on mixed winery wastewaters with initial sugars content of 50 g/L are not suitable because large amounts of unused sugars compounds remained in media after performed xanthan biosynthesis (Rončević et al, 2017). Therefore, the Figure 1.…”