Journal of Industrial Microbiology & Biotechnology最新文献

Effective microbial bioprocessing relies on maintaining ideal cultivation conditions, highlighting the necessity for tools that monitor and regulate cellular performance and robustness. This study evaluates a fed-batch cultivation control system based on at-line flow cytometry monitoring of intact yeast cells having a fluorescent transcription factor-based redox biosensor. Specifically, the biosensor assesses the response of an industrial xylose-fermenting Saccharomyces cerevisiae strain carrying the TRX2p-yEGFP biosensor for NADPH/NADP+ ratio imbalance when exposed to furfural. The developed control system successfully detected biosensor output and automatically adjusted furfural feed rate, ensuring physiological fitness at high furfural levels. Moreover, the single-cell measurements enabled the monitoring of subpopulation dynamics, enhancing control precision over traditional methods. The presented automated control system highlights the potential of combining biosensors and flow cytometry for robust microbial cultivations by leveraging intracellular properties as control inputs.

The filamentous fungus Trichoderma reesei is a mesophilic ascomycete commercially used to produce industrial enzymes for a variety of applications. Strain improvement efforts over many years have resulted in more productive hosts, but also in undesirable traits such as the need for lower temperatures to achieve maximum protein secretion rates. Lower fermentation temperatures increase the need for cooling resulting in higher manufacturing costs. We used a droplet-based evolution strategy to increase the protein secretion temperature of a highly productive T. reesei whole cellulase strain from 25°C to 28°C by first isolating an improved mutant and subsequently tracing the causative high temperature mutation to one gene designated gef1. An industrial host with a gef1 deletion was found to be capable of improved productivity at higher temperature under industrially relevant fermentation conditions.

Fermentation of pectin-rich biomass by Saccharomyces cerevisiae can produce bioethanol as a fuel replacement to combat carbon dioxide emissions from the combustion of fossil fuels. S.cerevisiae UCDFST 09-448 produces its own pectinase enzymes potentially eliminating the need for commercial pectinases during fermentation. This research assessed growth, pectinase activity, and fermentative activity of S. cerevisiae UCDFST 09-448 and compared its performance to an industrial yeast strain, S. cerevisiae XR122N. S. cerevisiae UCDFST 09-448's growth was inhibited by osmotic stress (xylose concentrations above 1M), ethanol concentrations greater than 5% v/v, and temperatures outside of 30°C-37°C. However, S. cerevisiae UCDFST 09-448 was able to consistently grow in an industrial pH range (3-6). It was able to metabolize glucose, sucrose, and fructose but was unable to metabolize arabinose, xylose, and galacturonic acid. The pectinase enzyme produced by S. cerevisiae UCDFST 09-448 was active under typical fermentation conditions (35°C-37°C, pH 5.0). Regardless of S. cerevisiae UCDFST 09-448's limitations when compared to S. cerevisiae XR122N in 15% w/v peach fermentations, S. cerevisiae UCDFST 09-448 was still able to achieve maximum ethanol yields in the absence of commercial pectinases (44.7 ± 3.1g/L). Under the same conditions S. cerevisiae XR122N produced 39.5 ± 3.1g/L ethanol. While S. cerevisiae UCDFST 09-448 may not currently be optimized for industrial fermentations, it is a step towards a consolidated bioprocessing approach to fermentation of pectin-rich biomass.

Pyrroquinoline quinone (PQQ) is one of the important coenzymes in living organisms. In acetic acid bacteria (AAB) it plays a crucial role in alcohol respiratory chain, as a coenzyme of alcohol dehydrogenase. In this work, the PQQ biosynthetic genes were overexpressed in Acetobacter pasteurianus CGMCC 3089 to improve the fermentation performance. The result shows that the intracellular and extracellular PQQ contents in the recombinant strain A. pasteurianus (pBBR1-p264-pqq) were 152.53% and 141.08% higher than those of the control A. pasteurianus (pBBR1-p264), respectively. The catalytic activity of alcohol dehydrogenase and aldehyde dehydrogenase increased by 52.92% and 67.04%, respectively. The results indicated that the energy charge and intracellular ATP were also improved in the recombinant strain. The acetic acid fermentation was carried out using a 5 L self-aspirating fermenter, and the acetic acid production rate of the recombinant strain was 23.20% higher compared with the control. Furthermore, the relationship between the PQQ and acetic acid tolerance of cells was analyzed. The biomass of recombinant strain was 180.2%, 44.3%, and 38.6% higher than those of control under 2%, 3%, and 4% acetic acid stress, respectively. After treated with 6% acetic acid for 40 min, the survival rate of the recombinant strain was increased by 76.20% compared with the control. Those result demonstrated that overexpression of PQQ biosynthetic genes increased the content of PQQ, therefore improving the acetic acid fermentation and the cell tolerance against acetic acid by improving the alcohol respiratory chain and energy metabolism.