Impacts of mixing on foaming, methane production, stratification and microbial community in full-scale anaerobic co-digestion process

© 2019 Elsevier Ltd This study investigated the impact of mixing on key factors including foaming, substrate stratification, methane production and microbial community in three full scale anaerobic digesters. Digester foaming was observed at one plant that co-digested sewage sludge and food waste, and was operated without mixing. The lack of mixing led to uneven distribution of total chemical oxygen demand (tCOD) and volatile solid (VS) as well as methane production within the digester. 16S rRNA gene-based community analysis clearly differentiated the microbial community from the top and bottom. By contrast, foaming and substrate stratification were not observed at the other two plants with internal circulation mixing. The abundance of methanogens (Methanomicrobia) at the top was about four times higher than at the bottom, correlating to much higher methane production from the top verified by ex-situ biomethane assay, causing foaming. This result is consistent with foaming potential assessment of digestate samples from the digester

Methyl Jasmonate and Methyl-β-Cyclodextrin Individually Boost Triterpenoid Biosynthesis in <i>Chlamydomonas Reinhardtii</i> UVM4.

The commercialisation of valuable plant triterpenoids faces major challenges, including low abundance in natural hosts and costly downstream purification procedures. Endeavours to produce these compounds at industrial scale using microbial systems are gaining attention. Here, we report on a strategy to enrich the biomass of the biotechnologically-relevant Chlamydomonas reinhardtii strain UVM4 with valuable triterpenes, such as squalene and (S)-2,3-epoxysqualene. C. reinhardtii UVM4 was subjected to the elicitor compounds methyl jasmonate (MeJA) and methyl-β-cyclodextrine (MβCD) to increase triterpene yields. MeJA treatment triggered oxidative stress, arrested growth, and altered the photosynthetic activity of the cells, while increasing squalene, (S)-2,3-epoxysqualene, and cycloartenol contents. Applying MβCD to cultures of C. reinhardtii lead to the sequestration of the two main sterols (ergosterol and 7-dehydroporiferasterol) into the growth medium and the intracellular accumulation of the intermediate cycloartenol, without compromising cell growth. When MβCD was applied in combination with MeJA, it counteracted the negative effects of MeJA on cell growth and physiology, but no synergistic effect on triterpene yield was observed. Together, our findings provide strategies for the triterpene enrichment of microalgal biomass and medium

Nodal dynamics, not degree distributions, determine the structural controllability of complex networks

Structural controllability has been proposed as an analytical framework for making predictions regarding the control of complex networks across myriad disciplines in the physical and life sciences (Liu et al., Nature:473(7346):167-173, 2011). Although the integration of control theory and network analysis is important, we argue that the application of the structural controllability framework to most if not all real-world networks leads to the conclusion that a single control input, applied to the power dominating set (PDS), is all that is needed for structural controllability. This result is consistent with the well-known fact that controllability and its dual observability are generic properties of systems. We argue that more important than issues of structural controllability are the questions of whether a system is almost uncontrollable, whether it is almost unobservable, and whether it possesses almost pole-zero cancellations.Comment: 1 Figures, 6 page

Manufacturing flow line systems: a review of models and analytical results

The most important models and results of the manufacturing flow line literature are described. These include the major classes of models (asynchronous, synchronous, and continuous); the major features (blocking, processing times, failures and repairs); the major properties (conservation of flow, flow rate-idle time, reversibility, and others); and the relationships among different models. Exact and approximate methods for obtaining quantitative measures of performance are also reviewed. The exact methods are appropriate for small systems. The approximate methods, which are the only means available for large systems, are generally based on decomposition, and make use of the exact methods for small systems. Extensions are briefly discussed. Directions for future research are suggested.National Science Foundation (U.S.) (Grant DDM-8914277

Whole-cell Biosensors for Monitoring Bioremediation

Whole-cell biosensors are sensing devices that typically use biofilm-dwelling microorganisms to detect specific physical or chemical aspects of environmental samples. Microbial detection produces a signal that is transformed into user accessible data which can be as simple as colour change on a paper strip or as complex as quantitative digital display. Whole-cells can be embedded on a transducer or used separately as part of a multi-step assay format. Both unmodified and genetically modified cells have been used in this way. Metabolic reporters are used to detect toxicity that inhibits cell metabolism while catabolic reporters can be used to detect specific contaminants. Biosensors can provide data on the bioavailability of contaminants and are very relevant to monitoring bioremediation. Several commercially available sensors have been developed and some of these have been widely tested and demonstrated to be effective at measuring environmental contaminants

Selection and stability of anode respiring bacteria biofilms

Engineering anode respiring bacteria (ARB) biofilms for optimal performance in microbial fuel cells (MFC) and biosensors is an emerging challenge. The structure of ARB biofilm community can be manipulated under stringent conditions. However, in most practical applications, the biofilms would need to operate in conditions quite different from those of the selection process and this could cause changes in community structure and consequently a loss of functionality. In this study, we tested whether anodic biofilms selected in specific conditions, would retain their community structure and electrochemical properties when operating long term in MFCs in conditions different from those used in the selection.This work was supported by funding to Lincoln Ventures Limited from the New Zealand Foundation for Research, Science and Technology, contract LVLX0802