Betaine removal during thermo- and mesophilic aerobic batch biodegradation of beet molasses vinasse: influence of temperature and pH on the progress and efficiency of the process

Efficiency of aerobic biodegradation of sugar beet distillery stillage under dissolved oxygen tension-controlled conditions

The efficiency of aerobic biodegradation of distillery wastewater using various microbial cultures is intricately linked to process conditions. The study aimed to examine the aerobic biodegradation by a Bacillus bacteria under controlled dissolved oxygen tension (DOT) conditions as a novel approach in the treatment of sugar beet distillery stillage. The processes were conducted in a 2-L Biostat®B stirred-tank reactor (STR), at a temperature of 36°C, with aeration of 1.0 L/(L·min), and uncontrolled pH of the medium (an initial pH of 8.0). Each experiment was performed at a different DOT setpoint: 75%, 65% and 55% saturation, controlled through stirrer rotational speed adjustments. The study showed that the DOT setpoint did not influence the process efficiency, determined by the pollutant load removal expressed as COD, BOD5 and TOC. In all three experiments, the obtained reduction values of these parameters were comparable, falling within the narrow ranges of 78.6-78.7%, 97.3-98.0% and 75.0-76.4%, respectively. However, the DOT setpoint did influence the rate of process biodegradation. The removal rate of the pollutant load expressed as COD, was the lowest when DOT was set at 55% (0.48 g O2/(L•h)), and the highest when DOT was set at 65% (0.55 g O2/(L•h)). For biogenic elements (nitrogen and phosphorus), a beneficial effect was observed at a low setpoint of controlled DOT during biodegradation. The maximum extent of removal of both total nitrogen (54%) and total phosphorus (67.8%) was achieved at the lowest DOT setpoint (55%). The findings suggest that conducting the batch aerobic process biodegradation of sugar beet stillage at a relatively low DOT setpoint in the medium might achieve high efficiency pollutant load removal and potentially lead to a reduction in the process cost.

Whether glycine betaine improves the thermotolerance of mesophilic anammox consortia

While the application of mesophilic anammox process is currently the state of the art, the feasibility of a thermophilic anammox bioprocess is still unclear. In this study, we investigate whether glycine betaine (GB) addition can enhance the thermotolerance of mesophilic anammox biomass in the upflow anaerobic sludge blanket (UASB) reactors fed with synthetic wastewater at a nitrogen loading of approximately 4 kg N m^-3 d^-1. The results showed that during a long-term operation at 45°C with GB (0, 0.1, 1, 2 mM) addition, anammox performance became worse with the final effluent concentrations of NO₂ ^-N of 145 ± 11.6 mg L^-1 and nitrogen removal efficiency decreased from 92.3-6.9%. Specific anammox activity decreased from 392.1 ± 12.1-6.0 ± 0.8 mg N g^-1 VSS d^-1, which were not significantly higher than those in the control reactor. The content of heme c showed a stronger downward trend in T₁ (with GB addition) than in the control reactor T₀. The qPCR results showed that the relative abundance of Candidatus Kuenenia decreased in both the experimental (from 53.5-28.8%) and control reactors (from 54.1-35.1%). Overall, continuous addition of exogenous GB did not improve the thermotolerance of mesophilic anammox consortia at 45°C.

Continuous process of aerobic biodegradation of beet molasses vinasse: focus on betaine removal

We analyzed the effect of hydraulic retention time (HRT) and pH control of beet molasses vinasse on the efficiency of its continuous aerobic biodegradation with a mixed culture of Bacillus bacteria. Two experimental series were conducted in a 2-L stirred-tank reactor, at an aeration rate of 1 vvm, stirrer speed of 900 rpm, and temperature of 36 °C. The first series was run without medium pH control, whereas the other with pH maintained at 8.0. In both series, HRTs were 26, 47, and 78 h, whereas vinasse pH was raised to 8.0. The extent of its treatment via aerobic biodegradation depended on betaine assimilation phenomenon. High removal of pollutants (over 84%) expressed by the SCODsum index (SCODsum = soluble COD determined with the dichromatic method + theoretical COD of betaine) was achieved at HRTs of 47 and 78 h, whereas medium pH control had no explicit effect on biodegradation efficiency.

Effect of pH and temperature on vinasse decolorization by lactic acid bacteria in batch processes

The waste-free policy is part of the process of sugar production from beets in which the resulting molasses are used for ethanol production. However, during this process another byproduct, namely vinasse, is created. Therefore, there is a problem with the utilization of wastewater, which cannot be disposed to the environment without being treated. Melanoidins, caramels, and hexoses alkaline degradation products contained in the vinasse give it a dark brown color. The aim of the study was to investigate the effect of the pH and the temperature on the decolorization of vinasse by lactic acid bacteria (Lactobacillus plantarum, L. casei, and Pediococcus parvulus). Experiments were performed in batch mode in a BioStatB bioreactor for 72 hrs. The medium consisted of 25% v/v sugar beet molasses vinasse, 77.34 gdm^-3 of glucose, and 2.24 gdm^-3 of yeast extract. The maximum decolorization was 25.14% and was achieved at noncontrolled pH 6.5 and at 30°C. PRACTITIONER POINTS: Lactobacillus plantarum, L. casei and Pediococcus parvulus showed potential for decolorization of sugar beet molasses vinasse. Controlled pH has a negative effect on sugar beet molasses vinasse decolorization. Toxic substances, i.e. acrylamide, 4-methylimidazole , 5-hydroxymethylfurfural and furfural after decolorization was not detected. Bacteria showed high degradation potential of 2-acetyl-4-(1,2,3,4)-tetrahydroxy-butylimidazole.

Biodegradation of main carbon sources in vinasse stillage by a mixed culture of bacteria: influence of temperature and pH of the medium

The aim of the study was to examine how temperature and the pH influence the progress and efficiency of an aerobic biodegradation process, where major organic pollutants are removed from beet molasses vinasse by a mixed culture of Bacillus bacteria. It was conducted in an aerated bioreactor with a stirring system in four experimental series, each composed of five processes run at temperatures of 27, 36, 45, 54 and 63 °C. In the first and second series, medium pH was not controlled, the initial pH amounted to 6.5 and 8.0, respectively. In the third and fourth series, medium pH was controlled at 6.5 and 8.0, respectively. Under optimal conditions, the pollution load of the vinasse stillage expressed as soluble chemical oxygen demand was removed with an 88.73% efficiency. The bacterial culture assimilated all organic pollutants simultaneously, but the rate of assimilation was different. An exception was the process of betaine assimilation, which intensified only when readily available carbon sources were depleted in the medium. Synthesis and assimilation of organic acids were observed in all experiments. Advantages of the proposed method include: possibility of its use at high temperatures, and no necessity for medium pH adjustment during the process.

Population heterogeneity in microbial bioprocesses: origin, analysis, mechanisms, and future perspectives

Population heterogeneity is omnipresent in all bioprocesses even in homogenous environments. Its origin, however, is only so well understood that potential strategies like bet-hedging, noise in gene expression and division of labour that lead to population heterogeneity can be derived from experimental studies simulating the dynamics in industrial scale bioprocesses. This review aims at summarizing the current state of the different parts of single cell studies in bioprocesses. This includes setups to visualize different phenotypes of single cells, computational approaches connecting single cell physiology with environmental influence and special cultivation setups like scale-down reactors that have been proven to be useful to simulate large-scale conditions. A step in between investigation of populations and single cells is studying subpopulations with distinct properties that differ from the rest of the population with sub-omics methods which are also presented here. Moreover, the current knowledge about population heterogeneity in bioprocesses is summarized for relevant industrial production hosts and mixed cultures, as they provide the unique opportunity to distribute metabolic burden and optimize production processes in a way that is impossible in traditional monocultures. In the end, approaches to explain the underlying mechanism of population heterogeneity and the evidences found to support each hypothesis are presented. For instance, population heterogeneity serving as a bet-hedging strategy that is used as coordinated action against bioprocess-related stresses while at the same time spreading the risk between individual cells as it ensures the survival of least a part of the population in any environment the cells encounter.

Performance and model of a novel multi-sparger multi-stage airlift loop membrane bioreactor to treat high-strength 7-ACA pharmaceutical wastewater: effect of hydraulic retention time, temperature and pH

In this study, three novel multi-sparger multi-stage airlift loop membrane bioreactors (Ms(2)ALMBRs) were set up in parallel for treating synthetic high-strength 7-ACA pharmaceutical wastewater under different HRTs, temperatures and pHs, respectively. During the 200-day operating time, average COD removal efficiencies were 94.96%, 96.05% and 93.9%. While average 7-ACA removal efficiencies were 66.44%, 59.04% and 59.60%, respectively. The optimal conditions were 10h, 15-35°C and 7-9 for HRT, temperature and pH, respectively. Moreover, the sludge characteristics and microorganism drug-resistances were explored. Results showed that different temperatures and pHs influenced contaminant removals by affecting MLSS concentration and β-lactamase activity significantly. In addition, mathematical statistical models, built on the polynomial and linear regression techniques, were developed for exploring the inner relationships between HRT, temperature and pH changes and MLSS concentrations, β-lactamase activities and contaminant removals of the Ms(2)ALMBR system.

The MetaCyc database of metabolic pathways and enzymes and the BioCyc collection of pathway/genome databases

The MetaCyc database (http://metacyc.org/) provides a comprehensive and freely accessible resource for metabolic pathways and enzymes from all domains of life. The pathways in MetaCyc are experimentally determined, small-molecule metabolic pathways and are curated from the primary scientific literature. MetaCyc contains more than 1800 pathways derived from more than 30,000 publications, and is the largest curated collection of metabolic pathways currently available. Most reactions in MetaCyc pathways are linked to one or more well-characterized enzymes, and both pathways and enzymes are annotated with reviews, evidence codes and literature citations. BioCyc (http://biocyc.org/) is a collection of more than 1700 organism-specific Pathway/Genome Databases (PGDBs). Each BioCyc PGDB contains the full genome and predicted metabolic network of one organism. The network, which is predicted by the Pathway Tools software using MetaCyc as a reference database, consists of metabolites, enzymes, reactions and metabolic pathways. BioCyc PGDBs contain additional features, including predicted operons, transport systems and pathway-hole fillers. The BioCyc website and Pathway Tools software offer many tools for querying and analysis of PGDBs, including Omics Viewers and comparative analysis. New developments include a zoomable web interface for diagrams; flux-balance analysis model generation from PGDBs; web services; and a new tool called Web Groups.