fed batch cultivation
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2021 ◽  
Vol 25 (6) ◽  
pp. 390-398
Author(s):  
Saba Karam ◽  
Mozhgan Raigani ◽  
Sahar Hassani Afshar ◽  
Yeganeh Talebkhan ◽  
Elham Bayat ◽  
...  

2021 ◽  
Author(s):  
Soong-bin Kang ◽  
Jong-Il Choi

Abstract Background: Corynebacterium glutamicum is used industrially to produce various bio-based organic acids. However, it is often cultivated under abiotic stress conditions, such as low pH, which can reduce both cell growth and the yield of the target compound. Here, a response regulator from Deinococcus radiodurans, DR1558, was introduced into a recombinant C. glutamicum strain expressing lysine decarboxylase (cadA) to enhance cadaverine production at acidic pHs.Results: During batch cultivation under acidic conditions, 6.4 g/L of cadaverine was produced by the recombinant C. glutamicum strain expressing cadA and dr1558; this yield was 1.7-fold higher than that produced by a recombinant C. glutamicum strain expressing only cadA. Transcriptional analysis revealed altered expression levels of stress defense- and cadaverine biosynthesis-related genes in the recombinant C. glutamicum strain expressing dr1558. During fed-batch cultivation, the recombinant C. glutamicum strain expressing cadA and dr1558 showed a 2.4-fold increase in cadaverine production compared to that produced by the recombinant C. glutamicum strain expressing only cadA. The cell growth of C. glutamicum expressing both cadA and dr1558 increased markedly during fed-batch cultivation at acidic pH.Conclusion: These results indicated that the response regulator dr1558 altered the expression of genes involved in metabolic pathways and stress defense mechanisms in C. glutamicum. Furthermore, C. glutamicum expressing the D. radiodurans dr1558 can be used to produce bio-based organic acids by fermentation in processes requiring acidic conditions.


Author(s):  
Xuelian Qi ◽  
Junlan Shao ◽  
Yinchu Cheng ◽  
Xiaoying He ◽  
Yan Li ◽  
...  

Abstract: 2-O-α-D-Glucopyranosyl-L-ascorbic acid (AA-2G) is an important industrial derivative of L-ascorbic acid (AA), which has the distinct advantages of non-reducibility, antioxidation, and reproducible decomposition into L-ascorbic acid and glucose. Enzymatic synthesis is a preferred method for AA-2G production over alternative chemical synthesis owing to the regioselective glycosylation reaction. α-Glucosidase, an enzyme classed into O- glycoside hydrolases, may be used in glycosylation reactions to synthesize AA-2G. Here, one α-glucosidase from Oryza sativa (rAGL) was recombinantly produced in Pichia pastoris GS115 and used for biosynthesis of AA-2G with few intermediates and byproducts. The extracellular rAGL reached 9.11 U/mL after fed-batch cultivation for 102 h in a 5-L fermenter. The specific activity of purified rAGL is 49.83 U/mg at 37 °C and pH 4.0. The optimal temperature of rAGL was 65 °C, and it was stable below 55 °C. rAGL was active over the range of pH 3.0–7.0, with the maximal activity at pH 4.0. Under the condition of 37 °C , pH 4.0, equimolar maltose and AA·Na, 8.7±0.4 g/L of AA-2G was synthesized by rAGL. These studies lay the basis for the industrial application of recombinant α-glucosidase. Keywords: α-Glucosidase; Oryza sativa; 2-O-α-D-glucopyranosyl-L-ascorbic acid; Transglycosylation; Pichia pastoris


2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Yang Zhang ◽  
Jie Peng ◽  
Huimin Zhao ◽  
Shuobo Shi

Abstract Background Production of biofuels and green chemicals by microbes is currently of great interest due to the increasingly limited reserves of fossil fuels. Biodiesel, especially fatty acid ethyl esters (FAEEs), is considered as an attractive alternative because of its similarity with petrodiesel and compatibility with existing infrastructures. Cost-efficient bio-production of FAEEs requires a highly lipogenic production host that is suitable for large-scale fermentation. As a non-model oleaginous yeast that can be cultured to an extremely high cell density and accumulate over 70% cell mass as lipids, Rhodotorula toruloides represents an attractive host for FAEEs production. Results We first constructed the FAEE biosynthetic pathways in R. toruloides by introducing various wax ester synthase genes from different sources, and the bifunctional wax ester synthase/acyl-CoA-diacyglycerol acyltransferase (WS/DGAT) gene from Acinetobacter baylyi was successfully expressed, leading to a production of 826 mg/L FAEEs through shake-flask cultivation. We then mutated this bifunctional enzyme to abolish the DGAT activity, and further improved the titer to 1.02 g/L. Finally, to elevate the performance of Δku70-AbWS* in a bioreactor, both batch and fed-batch cultivation strategies were performed. The FAEEs titer, productivity and yield were 4.03 g/L, 69.5 mg/L/h and 57.9 mg/g (mg FAEEs/g glucose) under batch cultivation, and 9.97 g/L, 90.6 mg/L/h, and 86.1 mg/g under fed-batch cultivation. It is worth mentioning that most of the produced FAEEs were secreted out of the cell, which should greatly reduce the cost of downstream processing. Conclusion We achieved the highest FAEEs production in yeast with a final titer of 9.97 g/L and demonstrated that the engineered R. toruloides has the potential to serve as a platform strain for efficient production of fatty acid-derived molecules.


Fermentation ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 62
Author(s):  
Konstantins Dubencovs ◽  
Janis Liepins ◽  
Arturs Suleiko ◽  
Anastasija Suleiko ◽  
Reinis Vangravs ◽  
...  

The Kluyveromyces marxianus yeast recently has gained considerable attention due to its applicability in high-value-added product manufacturing. In order to intensify the biosynthesis rate of a target product, reaching high biomass concentrations in the reaction medium is mandatory. Fed-batch processes are an attractive and efficient way how to achieve high cell densities. However, depending on the physiology of the particular microbial strain, an optimal media composition should be used to avoid by-product synthesis and, subsequently, a decrease in overall process effi-ciency. Thus, the aim of the present study was to optimise the synthetic growth medium and feeding solution compositions (in terms of carbon, nitrogen, phosphorous, magnesium, and calcium concentrations) for high cell density K. marxianus fed‑batch cultivations. Additionally, the biomass yields from the vitamin mixture and other macro/microelements were identified. A model predictive control algorithm was successfully applied for a fed-batch cultivation control. Biomass growth and substrate consumption kinetics were compared with the mathematical model predictions. Finally, 2‑phenylethanol biosynthesis was induced and its productivity was estimated. The determined optimal macronutrient ratio for K. marxianus biomass growth was identified as C:N:P = 1:0.07:0.011. The maximal attained yeast biomass concentration was close to 70 g·L-1 and the 2-PE biosynthesis rate was 0.372 g·L−1·h−1, with a yield of 74% from 2-phenylalanine.


Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 269
Author(s):  
Lijuan Zhong ◽  
Zheng Liu ◽  
Yinghua Lu

The aim of this study was to analyze the major influence factors of culture medium on the expression level of β-1,3-1,4-glucanase, and to further develop an optimized process for the extracellular production of β-glucanase at a bioreactor scale (7 L) with a genetically engineered Escherichia coli (E. coli) JM109-pLF3. In this study, batch cultivation and fed-batch cultivation including the constant rate feeding strategy and the DO-stat (DO: Dissolved Oxygen) feeding strategy were conducted. At a 7 L bioreactor scale for batch cultivation, biomass reached 3.14 g/L and the maximum β-glucanase activity was 506.94 U/mL. Compared with batch cultivation, the addition of glycerol, complex nitrogen and complete medium during fed-batch cultivation increased the production of biomass and β-1,3-1,4-glucanase. The maximum biomass and β-glucanase activity, which were 7.67 g/L and 1680 U/mL, respectively, that is, 2.45 and 3.31 times higher than those obtained with batch cultivation, were obtained by feeding a complex nitrogen source at a constant rate of 1.11 mL/min. Therefore, these nutritional supplements and strategies can be used as a reference to enhance the production of other bioproducts from E. coli.


2021 ◽  
Vol 13 ◽  
pp. 100634
Author(s):  
Priscila da Silva Delabona ◽  
Deise Juliana Lima ◽  
Carla Aloia Codima ◽  
Jonas Ramoni ◽  
Lucas Gelain ◽  
...  

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