Fermentation Titer Optimization and Impact on Energy and Water Consumption during Downstream Processing

Python-Based Algorithm for Calculating Physical Properties of Aqueous Mixtures Composed of Substances Not Available in Databases

In this study, we developed a Python-based open-source algorithm compatible with the aqueous physical property models provided in the electrolyte templates of AspenTech software. To validate the accuracy of the model, the results obtained from the proposed algorithm were compared to experimental data for 37 binary aqueous mixture systems covering properties such as density, heat capacity, viscosity, and thermal conductivity. The input variables included results from our previous research on pure component property prediction and the nonrandom two-liquid (NRTL) model parameters based on the UNIFAC model simulations. This open-source algorithm is compatible with AspenTech software. The mean absolute percentage errors (MAPE) for density, heat capacity, viscosity, and thermal conductivity were 2.88, 0.355, 12.1, and 10.1%, respectively. In the case of density and viscosity, the actual data trends could not be accurately reflected under high-concentration conditions for certain substances. In addition, it was confirmed that inaccurate predictions of the viscosity and thermal conductivity in the commercial-scale falling-film evaporator simulation for l-valine production led to inaccurate predictions of the overall heat transfer coefficient. Therefore, caution is required when predicting missing property parameters using this approach as significant errors may occur. Nevertheless, this algorithm can provide an initial parameter value for property models that are not included in existing databases without any commercial package.

High-efficiency water use and process performance for bioproduction of trans-cinnamic acid

Increasing water scarcity, driven by population growth and climate change, necessitates the development of biomanufacturing processes that maximize water-use efficiency. This report illustrates the potential of biocatalyst and supernatant recycling in a decoupled bioprocess integrated with product removal systems for trans-cinnamic production using Pseudomonas putida KT2440 expressing RmXAL. With a biocatalyst concentration of 40 gDCW L- 1 and an L-phenylalanine feed concentration of 35 gL-phe L- 1 combined with product precipitation, the process achieved a titer of 143.00 g L- 1, a production rate of 2.25 g L- 1 h- 1, a yield of 1.50 g tCA g glucose- 1, and a yield on L-phenylalanine of 0.64 g tCA g L-phe- 1. Furthermore, this optimized approach substantially reduced water consumption and wastewater generation by 85% compared to standard production processes, promoting the principles of Sustainable Development Goal 6 (SDG) "Clean water and sanitation" and SDG 12 "Responsible production and consumption" thus enabling an industrial bioproduction platform to achieve better environmental and economic sustainability.

Long-term effects of cycle time and volume exchange ratio on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production from food waste digestate by Haloferax mediterranei cultivated in sequencing batch reactors for 450 days

Food wastedigestatewas fed into a sequencing batch reactor (SBR) forHaloferax mediterranei(HM) to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). This SBR was operated uninterruptedly for 450 days to test its stability, during which the cycle time and volume exchange ratiowere varied to understand their impacts on the PHBV fermentation performance under ranged organic loading rates (OLR). Results showed that 1) PHBV productivity was proportional to OLR of food wastedigestate; 2) substrate and product inhibitions were two limiting factors constraining substrate utilization and PHBV yields; 3) PHBV titer was dependent on the hydraulic retention time of the SBR while a volume exchange ratio lower than 0.5 is unfavorable due to the product inhibitor accumulation. This study for the first time demonstrated that the long-term stability of food waste-fed PHBV production byHMand revealed that inhibition effects could be barriers in SBR limiting the full-scale application of the technology.

Tailoring non-axenic lactic acid fermentation from cheese whey permeate targeting a flexible lactic acid platform

Lactic acid (LA) is an important biobased platform chemical, with potential applications in synthetising a wide range of chemical products or serving as feedstock for various bioprocesses. Industrial LA production via pure culture fermentation is characterized by high operational costs and utilizes food-grade sugars, thereby reducing the feasibility of LA applications. In this context, our research focussed on valorising the largest dairy side stream, cheese whey permeate, through the use of mixed microbial communities. We evaluated the effect of different operational parameters (temperature, pH and hydraulic retention time) in non-axenic fermentations on productivity, yield, concentration, optical purity, and community. Our findings revealed that operating at mildly thermophilic conditions (45 °C) resulted in highly selective LA production, and significantly augmented the LA yield, and productivity, compared to higher temperatures (50-55 °C). In addition, operating at circumneutral pH conditions (6.0-6.5) led to significantly increased the LA fermentation performance compared to the conventional acid pH conditions (≤5.5). This led to an unprecedented LA productivity of 27.4 g/L/h with a LA yield of 70.0% which is 2.5 times higher compared to previous reported maximum. Additionally, varying pH levels influenced the optical purity of LA: we achieved an optical L-LA purity of 98.3% at pH 6.0-6.5, and an optical D-LA purity of 91.3% at a pH of 5.5. A short hydraulic retention time of less than 12 h was crucial for selective LA production. This process also yielded a microbial biomass composed of 90.3-98.6% Lactobacillus delbrueckii, which could be potentially valorised as probiotic or protein ingredient in food or feed products. Our work shows that by careful selection of operational conditions, the overall performance can be significantly increased compared to the state-of-the-art. These results highlight the potential of non-sterile LA fermentation and show that careful selection of simple reactor operation parameters can maximize process performance. A preliminary assessment suggests that valorising EU cheese whey permeate could increase LA and poly-LA production by 40 and 125 times, respectively. This could also lead to the production of 4,000 kton protein-rich biomass, potentially reducing CO2 emissions linked to EU food and feed production by 4.87% or 2.77% respectively.

Biosynthesis of natural and halogenated plant monoterpene indole alkaloids in yeast

Monoterpenoid indole alkaloids (MIAs) represent a large class of plant natural products with marketed pharmaceutical activities against a wide range of indications, including cancer, malaria and hypertension. Halogenated MIAs have shown improved pharmaceutical properties; however, synthesis of new-to-nature halogenated MIAs remains a challenge. Here we demonstrate a platform for de novo biosynthesis of two MIAs, serpentine and alstonine, in baker's yeast Saccharomyces cerevisiae and deploy it to systematically explore the biocatalytic potential of refactored MIA pathways for the production of halogenated MIAs. From this, we demonstrate conversion of individual haloindole derivatives to a total of 19 different new-to-nature haloserpentine and haloalstonine analogs. Furthermore, by process optimization and heterologous expression of a modified halogenase in the microbial MIA platform, we document de novo halogenation and biosynthesis of chloroalstonine. Together, this study highlights a microbial platform for enzymatic exploration and production of complex natural and new-to-nature MIAs with therapeutic potential.

Engineered Production of Isobutanol from Sugarcane Trash Hydrolysates in Pichia pastoris

Concerns over climate change have led to increased interest in renewable fuels in recent years. Microbial production of advanced fuels from renewable and readily available carbon sources has emerged as an attractive alternative to the traditional production of transportation fuels. Here, we engineered the yeast Pichia pastoris, an industrial powerhouse in heterologous enzyme production, to produce the advanced biofuel isobutanol from sugarcane trash hydrolysates. Our strategy involved overexpressing a heterologous xylose isomerase and the endogenous xylulokinase to enable the yeast to consume both C5 and C6 sugars in biomass. To enable the yeast to produce isobutanol, we then overexpressed the endogenous amino acid biosynthetic pathway and the 2-keto acid degradation pathway. The engineered strains produced isobutanol at a titer of up to 48.2 ± 1.7 mg/L directly from a minimal medium containing sugarcane trash hydrolysates as the sole carbon source. To our knowledge, this is the first demonstration of advanced biofuel production using agricultural waste-derived hydrolysates in the yeast P. pastoris. We envision that our work will pave the way for a scalable route to this advanced biofuel and further establish P. pastoris as a versatile production platform for fuels and high-value chemicals.

Candida glabrata Yap6 Recruits Med2 To Alter Glycerophospholipid Composition and Develop Acid pH Stress Resistance

Candida glabrata is a high-performance microbial cell factory for the production of organic acids. To elucidate the role of the C. glabrata Mediator tail subunit Med2 (CgMed2) at pH 2.0, we deleted or overexpressed CgMed2 and used transcriptome analysis to identify genes that are regulated by CgMed2. At pH 2.0, the deletion of CgMed2 resulted in a cell growth decrease of 26.1% and a survival decrease of 32.3%. Overexpression of CgMed2 increased cell growth by 12.4% and cell survival by 5.9% compared to the wild-type strain. Transcriptome and phenotypic analyses identified CgYap6 as a transcription factor involved in acid pH stress tolerance. Deletion of CgYap6 caused growth defects, whereas its overexpression enhanced cell growth at pH 2.0. Furthermore, total glycerophospholipid content and membrane integrity decreased by 33.4% and 21.8%, respectively, in the CgMed2Δ strain; however, overexpression of CgMed2 increased the total glycerophospholipid content and membrane integrity by 24.7% and 12.1%, respectively, compared with those of the wild-type strain at pH 2.0. These results demonstrated that under acid pH stress, CgMed2 physically interacts with CgYap6, which translocates from the cytoplasm to the nucleus after being phosphorylated by the protein kinase CgYak1. Once in the nucleus, CgYap6 recruits CgMed2 to express glycerophospholipid-related genes. Our study elucidated the function of CgMed2 under acid pH stress and provides a potential strategy to equip Candida glabrata with low-pH resistance during organic acid fermentation.IMPORTANCE This study investigated the function of the Mediator tail subunit CgMed2 in C. glabrata under low-pH stress. The protein kinase CgYak1 activates CgYap6 for the recruitment of CgMed2, which in turn increases glycerophospholipid content and membrane integrity to confer low-pH stress tolerance. This study establishes a new link between the Mediator tail subunit and transcription factors. Overall, these findings indicate that CgMed2 is a novel target to induce the low-pH stress response in C. glabrata.