New two-stage pH combined with dissolved oxygen control strategy for cyclic ß-1,2 glucans synthesis.

On the basis of a novel two-stage pH combined with dissolved oxygen (DO) control strategy in fed-batch fermentation, this research addresses the influence of pH on cyclic ß-1,2-glucans (CßGs) biosynthesis and melanin accumulation during the production of CßGs by Rhizobium radiobacter ATCC 13,333. Under these optimal fermentation conditions, the maximum cell concentration and CßGs concentration in a 7-L stirred-tank fermenter were 7.94 g L-1 and 3.12 g L-1, which were the maximum production reported for R. radiobacter. The melanin concentration of the fermentation broth was maintained at a low level, which was beneficial to the subsequent separation and purification of the CßGs. In addition, a neutral extracellular oligosaccharide (COGs-1) purified by the two-stage pH combined with DO control strategy fermentation medium was structurally characterized. Structural analyses indicated that COGs-1 was a family of unbranched cyclic oligosaccharides composed of only ß-1,2-linked D-glucopyranose residues with degree of polymerization between 17 and 23, namely CßGs. This research provides a reliable source of CßGs and structural basis for further studies of biological activity and function. KEY POINTS: • A two-stage pH combined with DO control strategy was proposed for CßGs production and melanin biosynthesis by Rhizobium radiobacter. • The final extracellular CßGs production reached 3.12 g L-1, which was the highest achieved by Rhizobium radiobacter. • The existence of CßGs could be detected by TLC quickly and accurately.

In Vitro Digestion and Fecal Fermentation of Low-Gluten Rice and Its Effect on the Gut Microbiota.

Low-gluten rice is part of a special diet for chronic kidney disease patients, but its digestive mechanism in the gastrointestinal tract is unclear. In this study, low-gluten rice (LGR), common rice (CR), and rice starch (RS) were used as experimental samples, and their digestion and bacterial fermentation were simulated using an in vitro gastrointestinal reactor to investigate the mechanism of the effect of LGR on human health. The starch digestibility of CR was higher than that of LGR, with statistically significant differences. LGR has growth-promoting and metabolic effects on Akkermansia muciniphila. Among the beneficial metabolites, the concentration of short-chain fatty acids (SCFAs) from LGR reached 104.85 mmol/L, an increase of 44.94% (versus RS) and 25.33% (versus CR). Moreover, the concentration of lactic acid reached 18.19 mmol/L, an increase of 60.55% (versus RS) and 25.28% (versus CR). Among the harmful metabolites, the concentration of branched-chain fatty acids (BCFAs) in LGR was 0.29 mmol/L and the concentration of ammonia was 2.60 mmol/L, which was 79.31% and 16.15% lower than CR, respectively. A significant increase in the concentration of the beneficial intestinal bacteria Bacteroides and Bifidobacterium occurred from LGR. The 16s rDNA sequencing showed that the abundance of the Bacteroidetes and Firmicutes increased and the abundance of the Proteobacteria and Fusobacteria decreased. Thus, LGR has positive effects on digestion and gut microbiota structure and metabolism in humans.

The effects of high-fat foods on gut microbiota and small molecule intestinal gases: release kinetics and distribution in vitro colon model.

Profiling intestinal gases and their responses to dietary changes can reveal the products and functions of the gut microbiota and their influence on human health. High-fat foods (HFF) can alter the gut microbiota and its metabolites, posing a potential health risk. However, little is known about the effects of HFF on intestinal gas distribution. Therefore, in this study, we used human fecal microorganisms as strains, an in vitro three-chamber colon model and an intestinal gas array sensor as tools. We performed in vitro fermentation using HFF as the fermentation substrate to reveal the effects of HFF on the kinetics of intestinal gas production and changes in the gut microbiota and its metabolites. We found that dietary fatty acids stimulated the production of H2S and volatile organic compounds in the colon, promoted Firmicutes abundance, and decreased Bacteroidetes abundance. These results highlight the potential role of HFF in altering the gut microbiota and intestinal gas, which can lead to health hazards.

In vitro digestion and fecal fermentation of highly resistant starch rice and its effect on the gut microbiota.

Highly resistant starch rice (HRSR) is of particular interest in terms of its capacity to deliver short-chain fatty acids (SCFAs) to the colon in the prevention of diabetes mellitus and obesity. In this study, HRSR was processed into cooked rice, rice milk, rice cake, and rice popcorn, and the in vitro digestion and fermentation processes were monitored. The results showed that the starch digestibility of the four samples conformed to a first-order two-phase equation, and the resistant starch content of rice cake was the highest (11.98%). Compared with inulin, rice cake had a slower fermentation rate, and the butyrate concentration increased by 67.85%. The abundances of Prevotellaceae, which promotes the synthesis of SCFAs, and anti-inflammatory Faecalibacterium increased. The abundances of Proteobacteria and Megamonas, markers of gut microbiota imbalance, decreased. The results might facilitate the design and production of functional food products for type 2 diabetic and obese patients and improving colonic health.

Study of growth, metabolism, and morphology of Akkermansia muciniphila with an in vitro advanced bionic intestinal reactor.

BACKGROUND: As a kind of potential probiotic, Akkermansia muciniphila abundance in human body is directly causally related to obesity, diabetes, inflammation and abnormal metabolism. In this study, A. muciniphila dynamic cultures using five different media were implemented in an in vitro bionic intestinal reactor for the first time instead of the traditional static culture using brain heart infusion broth (BHI) or BHI + porcine mucin (BPM). RESULTS: The biomass under dynamic culture using BPM reached 1.92 g/L, which improved 44.36% compared with the value under static culture using BPM. The biomass under dynamic culture using human mucin (HM) further increased to the highest level of 2.89 g/L. Under dynamic culture using porcine mucin (PM) and HM, the main metabolites were short-chain fatty acids (acetic acid and butyric acid), while using other media, a considerable amount of branched-chain fatty acids (isobutyric and isovaleric acids) were produced. Under dynamic culture Using HM, the cell diameters reached 999 nm, and the outer membrane protein concentration reached the highest level of 26.26 µg/mg. CONCLUSIONS: This study provided a preliminary theoretical basis for the development of A. muciniphila as the next generation probiotic.

Multi-stage glucose/pachymaran co-feeding enhanced endo-ß-1,3-glucanase production by Trichoderma harzianum via simultaneous increases in cell concentration and inductive effect.

Endo-ß-1,3-glucanase is used to hydrolyze curdlan in a wide range of oligosaccharides production processes. Using pachymaran as the sole carbon source resulted in an endo-ß-1,3-glucanase activity of 86.1 U/mL and an Eendo/Etotal ratio of 0.43, which were 3.2 and 1.65 folds of the values from control (glucose as the sole carbon source), due to the inductive effect of pachymaran as a polysaccharide. However, the cell concentration decreased from 25 to 12 g/L during the late fermentation phase. Therefore, a novel multi-stage feeding strategy was developed wherein glucose was fed twice during the cell logarithmic growth phase (24 and 48 h) and pachymaran once during the early stage of the enzyme accumulation phase (72 h). Consequently, the cell concentration remained around 30 g/L during the late fermentation phase. Endo-ß-1,3-glucanase activity and Eendo/Etotal reached 160.0 U/mL and 0.76, respectively, which were 6.0 and 2.92 folds of the values from control. In addition, three typical polysaccharides with ß-1,3-linked glucose residues were successfully hydrolyzed by endo-ß-1,3-glucanase to produce multifunctional ß-1,3-oligoglucosides.

Prognostic values of lymphocyte and eosinophil counts in resectable cervical squamous cell carcinoma.

Aim: Cervical cancer is one of the leading causes of cancer mortality in women. Peripheral white blood cell parameters such as neutrophil (NE), eosinophil (EO), basophil (BA), as well as lymphocyte (LY) and monocyte (MO), are correlated with tumor outcomes. Methods: In total, 110 cervical squamous cell carcinoma patients were recruited in this study. The potential prognostic factors were evaluated by univariate and multivariate survival analysis. Results: Cox regression analysis model indicated that higher pretreatment EO level and increased post-/preradiotherapy EO ratio were independently associated with worse progression-free survival. Lower pretreatment LY or higher EO levels and increased post-/preradiotherapy EO ratio were independently associated with worse overall survival. Conclusion: LY and EO are correlated with outcomes of cervical squamous cell cancer.

Prognostic Values of Systemic Inflammation Response (SIR) Parameters in Resectable Cervical Cancer.

BACKGROUND: Cervical carcinoma is the leading cause of cancer mortality in women. C-reactive protein (CRP), albumin (ALB), globulin (GLB), lactate dehydrogenase (LDH), and albumin-to-globulin ratio (AGR) are indicators of systemic inflammation response correlated with tumor outcomes. METHODS: This study recruited 110 patients with cervical cancer. The patients were divided into 2 groups according to pretreatment median values of CRP, ALB, GLB, LDH, and AGR. The post/preradiotherapy or post/pretreatment ratios were defined as rates of pretreatment CRP, ALB, GLB, LDH, and AGR values and the corresponding ones obtained after radiotherapy or whole treatment. RESULTS: Higher pretreatment CRP or LDH levels were correlated with worse progression-free survival (PFS) and overall survival (OS). Increased post/preradiotherapy CRP ratio was correlated with worse PFS and OS, increased post/preradiotherapy LDH ratio was correlated with worse PFS. Increased post/pretreatment CRP ratio was correlated with worse PFS and OS, not-increased post/pretreatment AGR ratio was correlated with worse OS. Cox regression analysis model indicated that, moderately or poorly of differentiation, higher pretreatment CRP or LDH levels were independently associated with worse PFS, higher pretreatment CRP or LDH levels and increased post/pretreatment CRP ratio were independently associated with worse OS. CONCLUSION: CRP, LDH, or AGR are correlated with outcomes of resectable cervical cancer.

High production of xanthan gum by a glycerol-tolerant strain Xanthomonas campestris WXLB-006.

The superior properties of xanthan gum make it an industrial aginomoto used in many industries, especially in oil recovery. In the present work, xanthan production from glycerol by a mutant strain Xanthomonas campestris WXLB-006 reached as high as 17.8 g/L in flask culture. With the adoption of pH control, varied aeration and agitation, and varied glycerol feeding strategy, xanthan production reached 33.9 g/L in a 7-L fermenter and fermentation time decreased to 60 hr. Instead of difficultly and costly purifying glycerol, this research provides a very good case for glycerol utilization. At the same time, this is the first report on a high glycerol-tolerant strain for microbial polysaccharide production and 33.9 g/L is the highest production of xanthan gum produced from glycerol so far.

Optimization of a low-cost hyperosmotic medium and establishing the fermentation kinetics of erythritol production by Yarrowia lipolytica from crude glycerol.

The production of erythritol by Yarrowia lipolytica from low-cost substitutable substrates for high yield was investigated. Crude glycerol, urea, and NaCl related to osmotic pressure were the most significant factors affecting erythritol production. An artificial neural network model and genetic algorithm were used to search the optimal composition of the significant factors and locate the resulting erythritol yield. Medium with 232.39 g/L crude glycerol, 1.57 g/L urea, and 31.03 g/L NaCl led to predictive maximum erythritol concentration of 110.7 g/L. The erythritol concentration improved from 50.4 g/L to 109.2 g/L with the optimized medium, which was reproducible. Erythritol fermentation kinetics were investigated in a batch system. Multistep fermentation kinetic models with hyperosmotic inhibitory effects were developed. The resulting mathematical equations provided a good description of temporal variations such as microbial growth (X), substrate consumption (S), and product formation (P) in erythritol fermentation. The accordingly derived model is the first reported model for fermentative erythritol production from glycerol, providing useful information to optimize the growth of Y. lipolytica and contributing visual description for the erythritol fermentation process under high osmotic pressure, as well as improvement of productivity and efficiency.

Improving arachidonic acid fermentation by Mortierella alpina through multistage temperature and aeration rate control in bioreactor.

Effective production of arachidonic acid (ARA) using Mortierella alpina was conducted in a 30-L airlift bioreactor. Varying the aeration rate and temperature significantly influenced cell morphology, cell growth, and ARA production, while the optimal aeration rate and temperature for cell growth and product formation were quite different. As a result, a two-stage aeration rate control strategy was constructed based on monitoring of cell morphology and ARA production under various aeration rate control levels (0.6-1.8 vvm). Using this strategy, ARA yield reached 4.7 g/L, an increase of 38.2% compared with the control (constant aeration rate control at 1.0 vvm). Dynamic temperature-control strategy was implemented based on the fermentation performance at various temperatures (13-28°C), with ARA level in total cellular lipid increased by 37.1% comparing to a constant-temperature control (25°C). On that basis, the combinatorial fermentation strategy of two-stage aeration rate control and dynamic temperature control was applied and ARA production achieved the highest level of 5.8 g/L.

Improving Performance and Operational Stability of Porcine Interferon-α Production by Pichia pastoris with Combinational Induction Strategy of Low Temperature and Methanol/Sorbitol Co-feeding.

Various induction strategies were investigated for effective porcine interferon-α (pIFN-α) production by Pichia pastoris in a 10 L fermenter. We found that pIFN-α concentration could be significantly improved with the strategies of low-temperature induction or methanol/sorbitol co-feeding. On this basis, a combinational strategy of induction at lower temperature (20 °C) with methanol/sorbitol co-feeding has been proposed for improvement of pIFN-α production. The results reveal that maximal pIFN-α concentration and antiviral activity reach the highest level of 2.7 g/L and 1.8 × 10(7) IU/mg with the proposed induction strategy, about 1.3-2.1 folds higher than those obtained with other sub-optimal induction strategies. Metabolic analysis and online multi-variable measurement results indicate that energy metabolic enrichment is responsible for the performance enhancement of pIFN-α production, as a large amount of ATP could be simultaneously produced from both formaldehyde oxidation pathway in methanol metabolism and tricarboxylic acid (TCA) cycle in sorbitol metabolism. In addition, the proposed combinational induction strategy enables P. pastoris to be resistant to high methanol concentration (42 g/L), which conceivably occur associating with the error-prone methanol over-feeding. As a result, the proposed combinational induction strategy simultaneously increased the targeted protein concentration and operational stability leading to significant improvement of pIFN-α production.

A novel osmotic pressure control fed-batch fermentation strategy for improvement of erythritol production by Yarrowia lipolytica from glycerol.

The effect of osmotic pressure on erythritol and mannitol production by an osmophilic yeast strain of Yarrowia lipolytica CICC 1675 using glycerol as the sole carbon source was investigated. Appropriately high osmotic pressure was found to enhance erythritol production and inhibit mannitol formation. A novel two-stage osmotic pressure control fed-batch strategy based on the kinetic analysis was developed for higher erythritol yield and productivity. During the first 96 h, the osmotic pressure was maintained at 4.25 osmol/kg by feeding glycerol to reduce the inhibition of cell growth. After 132 h, the osmotic pressure was controlled at 4.94 osmol/kg to maintain a high dp(ery)/dt. Maximum erythritol yield of 194.3g/L was obtained with 0.95 g/L/h productivity, which were 25.7% and 2.2%, respectively, improvement over the best results in one-stage fed-batch fermentation. This is the first report that a novel osmotic pressure control fed-batch strategy significantly enhanced erythritol production.

Enhancing pIFN-α production and process stability in fed-batch culture of Pichia pastoris by controlling the methanol concentration and monitoring the responses of OUR/DO levels.

Effective expression of porcine interferon-α (pIFN-α) with recombinant Pichia pastoris was conducted in a bench-scale fermentor using an in situ methanol electrode-based feeding process with the control level of methanol concentration linearly increased to 10 g l⁻¹ for the first 20 h and maintained at 10 g l⁻¹ for the rest of expression phase. With this two-stage control process, the highest pIFN-α concentration reached a level of 1.81 g l⁻¹, which was 1.5-fold of that in the previous constant 10 g l⁻¹ induction experiments. There is an improvement of the pIFN-α productivity from more distribution of carbon flux to protein expression. The pIFN-α expression stability could be further enhanced by a simple on-line fault diagnosis method for methanol overfeeding based on oxygen uptake rate changing patterns. By implementing corrective action of feeding glycerol after fault detection, the production yield increased to twice the amount it would have been without the diagnosis.

Methanol/sorbitol co-feeding induction enhanced porcine interferon-α production by P. pastoris associated with energy metabolism shift.

The production of porcine interferon-α (pIFN-α) by Pichia pastoris was largely enhanced when adopting sorbitol/methanol co-feeding induction strategy at 30 °C in a 10-L fermentor. Analysis of energy regeneration pattern and carbon metabolism revealed that major energy metabolism energizing pIFN-α synthesis shifted from formaldehyde dissimilatory energy metabolism pathway to TCA cycle under the methanol/sorbitol co-feeding induction strategy. The sorbitol/methanol co-feeding induction strategy weakened formaldehyde dissimilatory pathway and repressed the accumulation of toxic metabolite-formaldehyde, reduced theoretical oxygen consumption rate and oxygen supply requirement, and increased energy/methanol utilization efficiency so that more methanol could be effectively used for pIFN-α synthesis. As a result, pIFN-α antiviral activity reached a highest level of 1.8 × 10(7) IU/mL which was about 10- to 200-folds of those obtained under pure methanol induction at 20 and 30 °C, respectively.

Improvement of specific growth rate of Pichia pastoris for effective porcine interferon-α production with an on-line model-based glycerol feeding strategy.

Effective expression of porcine interferon-α (pIFN-α) with recombinant Pichia pastoris was conducted in a bench-scale fermentor. The influence of the glycerol feeding strategy on the specific growth rate and protein production was investigated. The traditional DO-stat feeding strategy led to very low cell growth rate resulting in low dry cell weight (DCW) of about 90 g/L during the subsequent induction phase. The previously reported Artificial Neural Network Pattern Recognition (ANNPR) model-based glycerol feeding strategy improved the cell density to 120 g DCW/L, while the specific growth rate decreased from 0.15 to 0.18 to 0.03-0.08 h(-1) during the last 10 h of the glycerol feeding stage leading to a variation of the porcine interferon-α production, as the glycerol feeding scheme had a significant effect on the induction phase. This problem was resolved by an improved ANNPR model-based feeding strategy to maintain the specific growth rate above 0.11 h(-1). With this feeding strategy, the pIFN-α concentration reached a level of 1.43 g/L, more than 1.5-fold higher than that obtained with the previously adopted feeding strategy. Our results showed that increasing the specific growth rate favored the target protein production and the glycerol feeding methods directly influenced the induction stage. Consequently, higher cell density and specific growth rate as well as effective porcine interferon-α production have been achieved by our novel glycerol feeding strategy.