This type of treatment may cause serious metabolic stress in the yeast cells, decreasing their viability https://www.selleckchem.com/products/GDC-0941.html . Another alternative to control microbial contamination is the pre-treatment of the fermentation substrate (sugar cane juice and molasses) by pasteurization. It can reduce bacterial contamination to lower levels (ca. 103 cells/ml), but the high costs for cooling the substrate is not economically viable. Industrial antibiotics are also frequently used by many distilleries in the pre-fermentation stage, in spite of possible
environmental impacts they may cause . Bacterial contamination appears to reduce the process productivity, by reducing yeast growth, viability, and fermentation capacity [6, 7]. Lactic Acid Bacteria (LAB) are very abundant this website in the bioethanol process possibly because of their VEGFR inhibitor tolerance to ethanol, low pH
and high temperature . Lactic and acetic acids produced by LAB may interfere in the yeast metabolism . Proliferation of LAB in the fermentation tanks is often unpredictable, leading to shut down of the refinery for cleaning and desinfection. The proliferation of LAB has indeed a negative effect in the process and may cause serious economic losses. Therefore, it is crucial to have a better understanding of the abundance and diversity of LAB throughout the bioethanol process in order to design more efficient production processes. To our knowledge, this is the first study in Northeast Brazilian distilleries aiming at the characterization of the bioethanol process microbiota. The aim of the present study was to analyze the abundance and diversity of LAB in the bioethanol process. Four representative distilleries (Japungu, Miriri, Giasa
and Trapiche) in Northeast Brazil were monitored between 2007 and 2008. Results The total mean number of CFUs in Japungu, Miriri, Giasa and Trapiche varied between 3.7 × 107 and 1.2 × 108, 7.5 × 106 and 8.9 × 107, 6.0 × 105 Methamphetamine and 8.9 × 108, and 1.8 × 107 and 5.9 × 108, respectively (Figure 1). Crude sugar cane juice contained 7.4 × 107 to 6.0 × 108 LAB CFUs. Juice cane LAB isolates were not identified in this study. Ethanol content in the process varied between 5.9 and 7.9%. A total of 489 putative LAB isolates were obtained from the fermentation tanks of four distilleries (additional file 1). The screening of the 489 presumptive LAB isolates by means of restriction enzyme analysis of rRNA operon allowed the rapid presumptive identification of the species found in the bioethanol process. The detailed reference restriction pattern of each species (additional file 2) and examples of L. vini and L. fermentum patterns are presented (Figure 2). The typical patterns contained three diagnostic bands (between 500 and 1000 bp).