Yeast Extract Supplementation Research Articles

Effect of nutrient supplements on molasses fermentation by salt preconditioned cells of Saccharomyces cerevisiae

Molasses, the major by-product of sugarcane processing industry, is an efficient and economical source for ethanol production. In the present work, the effect of yeast extract, tween-80 and ergosterol on molasses fermentation was studied using salt preconditioned Saccharomyces cerevisiae MTCC 11815 cells. Design expert 10.0 software under RSM plan was used to optimize the nutrient concentrations and four responses viz. residual brix, ethanol, glycerol and trehalose produced were recorded. Thus, with optimized nutrient concentrations, the salt preconditioned cells showed significantly better ethanol production (11.45%, v/v) as compared to controls viz. preconditioned un-supplemented cells (9.92%, v/v) and unconditioned cells (8.13%, v/v). Further, the molasses fermentation was validated at 10L scale and 11.67% (v/v) of ethanol was produced with 86.83% fermentation efficiency with 0.523% (w/v), 0.251% (v/v) and 3.8mg/100ml of yeast extract, tween-80 and ergosterol supplementation, respectively.

A Comprehensive Study on IAA production by Bradyrhizobium japonicum and Bacillus subtilis and Its Effect on Vigna radiata Plant Growth

Background: The use of chemical fertilizers and pesticides raises concerns about environmental pollution, health hazards and the destruction of biotic groups that support plant growth. Plant growth-promoting rhizobacteria (PGPR) thrive in the rhizosphere of plants are the auspicious alternative for these chemicals. PGPR plays a critical role in plant growth and development, along with biocontrol activities. Methods: In this present study, two effective microbes, Bradyrhizobium japonicum and Bacillus subtilis were chosen and their ability to produce Indole Acetic acid (IAA) was determined. Optimization of IAA production was carried out in different cultural conditions. Further, in-vitro studies were carried out to analyze the effect of these bacteria on the growth of Vigna radiata. Results: Our investigations showed that both organisms have the potential to produce IAA under standard conditions. IAA production is maximum when using Bradyrhizobium japonicum with the supplement of Carboxymethyl cellulose and yeast extract as C and N source, respectively. L-Tryptophan concentration has a positive effect on production. Further, the application of bacterial cultures has shown more significant improvement in plant growth in terms of root and shoot length and weight of crop material. The current findings recommend that Bradyrhizobium japonicum can be a suitable organism for application as a plant growth promoter.

Effects of yeast and yeast extract on growth performance, antioxidant ability and intestinal microbiota of juvenile Pacific white shrimp (Litopenaeus vannamei)

An 8-week feeding trial was proceeded to assess the effects of yeast and yeast extract on growth performance, anti-oxidant ability and intestinal microbiota of Litopenaeus vannamei. Five diets supplemented with 0% (Control), 3% beer yeast (Y), 0.5% yeast extract (YE0.5), 1% yeast extract (YE1) and 2% yeast extract (YE2) respectively were assigned to L. vannamei (four replicates per diet, 30 shrimp in each replicate, initial body weight 1.38 ± 0.01 g). The results showed higher weight gain and specific growth rate in shrimp fed diet YE2 compared with those fed the Control (P < .05). Both dietary yeast and yeast extract increased condition factor of shrimp (P < .05). Whole body moisture was significantly lower in shrimp fed yeast and yeast extract than those fed diet Control (P < .05). Shrimp fed yeast extract showed higher total antioxidant capacity compared to Control group (P < .05). Shrimp fed diet YE2 obtained higher catalase and glutathione peroxidase activities than those fed diet Control, YE0.5 and YE1 (P < .05). The main phyla in intestine of shrimp were Tenericutes, Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria. With the increasing dietary yeast extract supplementation, the relative abundances of Ruegeria, and its belonging Rhodobacteraceae, Rhodobacterales, Alphaproteobacteria, Proteobacteria in intestine increased gradually, which were significantly higher than those fed diet Control and Y (P < .05). Moreover, yeast and yeast extract significantly increased the Shannon indexes of intestinal microbiota (P < .05). Overall, dietary 2.0% yeast extract supplementation significantly increased growth performance and antioxidant ability of shrimp, also enhanced microbial diversity and microbiota structure in intestine of L. vannamei.

Evaluating metabolic potential of Thauera sp. M9 for the transformation of 4-chloroaniline (4-CA)

Abstract Thauera sp. M9, was isolated after enrichment of microbial diversity in nitrogen free mineral salt medium (NFMSM) supplemented with 300 mg/l of 4-chloroaniline (4-CA). The isolate M9 was able to achieve complete degradation of 300 mg/l 4-CA supplement to NFMSM, after 30 h incubation. In addition to 4-CA, isolate M9 was able to achieve complete degradation of 300 mg/l 3-chloroaniline (3-CA), 21% degradation of 300 mg/l 2-chloroaniline (2-CA), and complete transformation of 50 mg/l of 3, 4-dichloroaniline (3, 4-DCA), was observed only in the presence of 0.02% (w/v) yeast extract (YE) supplement to NFMSM. The presence of catechol 2, 3-dioxygenase (C23O) activity in cell free extract and detection of 4-chlorocatechol (4-CC); 2-hydroxy muconic semialdehyde (2-HMS) in biologically transformed samples by mass spectroscopy (MS) analysis indicated to meta-cleavage of the aromatic ring. A plug flow reactor (PFR) was developed using polyurethane foam (PUF) and refractory brick pieces (RBP) as immobilization matrix. The treatment of simulated effluent supplemented with 300 mg/l 4-CA through PFR, resulted in 88% transformation of 4-CA and 70% lowering of chemical oxygen demand (COD). These observations suggest that Thauera sp. M9 could be a potential inoculum for developing bioremediation protocols for waste rich in chloroanilines (CAs).

Nattokinase production from Bacillus subtilis using cheese whey: Effect of nitrogen supplementation and dynamic modelling

In this study, cheese whey – a nutrient-rich industrial waste was utilized as a low-cost fermentation medium for the growth of Bacillus subtilis and nattokinase production. The nattokinase yield (caseinolytic activity) using cheese whey (789.93 U ml−1) was 5 %–7 % less compared to glucose- or lactose-based synthetic media (833.44 and 850.84 U ml−1, respectively). Effect of nitrogen supplementation (yeast extract, tryptone, and peptone) on nattokinase yield was tested adopting an L9 (33) Taguchi experimental design, which revealed yeast extract as the best nitrogen source. Yeast extract supplementation (10 g l-1) to cheese whey increased the caseinolytic activity to 833.43 U ml−1, making it comparable to lactose- and glucose-based synthetic media, while lowering the medium cost by 55–60 %. A dynamic model incorporating logistic growth, substrate utilization and Luedeking-Piret product formation kinetics across all carbon-sources offered good agreement (R2 > 0.93). The estimated maximum specific growth rate on lactose-based synthetic medium (0.204 h−1), or yeast extract supplemented cheese whey medium (0.201 h−1) were better than that of the glucose-based synthetic medium (0.122 h−1). A similar observation on the growth associated product formation parameters offers insight on medium selection process. Overall, this study suggested that cheese whey could be utilized as a low-cost medium for nattokinase production.

Effects of process conditions and yeast extract on the synthesis of selenium nanoparticles by a novel indigenous isolate Bacillus sp. EKT1 and characterization of nanoparticles.

Selenium nanoparticles (SeNPs) are attractive nanomaterials for application in medical diagnosis, because their toxicities are lower than the elemental selenium which is a functional element and essential for human. In the current study, SeNPs synthesis capability of a novel soil originated indigenous Bacillus isolate was investigated. In this context, effects of processing conditions (SeO2 concentration, pH, temperature, and time), and yeast extract supplementation on the synthesis of SeNPs have been tested. In addition, nanoparticles were characterized and antioxidant capacity was determined. The cell-free supernatant of the bacterium, which was obtained after the cultivation of the isolate in nutrient broth at 33°C for 24h, was used for the synthesis. During the synthesis color change from light yellow to red-orange was an indication of the formation of SeNPs. Effect of SeO2 concentration was tested on the formation of nanoparticles and at concentrations higher than 10mM, there was no formation of nanoparticles. The best production was achieved at 6.4mM concentration, at pH 9 and 33°C in 72h. Field emission scanning electron microscopy (FESEM) images revealed that SeNPs were spherical in shape having the diameters between 31 and 335nm, and the average diameter was determined to be 126nm. Energy dispersive X-ray spectroscopy analysis confirmed the presence of elemental selenium. SeNPs possessed significant antioxidant activity that the scavenging capacity was up to 56.5 ± 5% (IC50 322.8μg/mL).

Preliminary Investigation of Utilization of a Cellulose-Based Polymer in Enhanced Oil Recovery by Oilfield Anaerobic Microbes and its Impact on Carbon Steel Corrosion

Water injection increases reservoir pressure in enhanced oil recovery (EOR). Among other oilfield performance chemicals, an EOR polymer is added to the injection water to provide the viscosity necessary for effective displacement of viscous crude oil from the reservoir formation. However, these organic macromolecules may be degraded by microbes downhole, causing undesirable viscosity loss. The organic carbon utilization by the microbes promotes microbial metabolism, thus potentially exacerbating microbiologically influenced corrosion (MIC). In this preliminary laboratory investigation, 3,000 ppm (w/w) carboxymethyl cellulose sodium (CMCS), a commonly used EOR polymer, was found to be utilized by an oilfield biofilm consortium. This oilfield biofilm consortium consisted of bacteria (including that can degrade large organic molecules), sulfate-reducing bacteria (SRB), and other microorganisms. A 30-day incubation in 125 mL anaerobic vials was conducted with an artificial seawater medium without yeast extract and lactate supplements at 37°C. The polymer biodegradation led to 16% viscosity loss in the broth and a 30× higher SRB sessile cell count. Slightly increased MIC weight loss and pitting corrosion were observed on C1018 carbon steel coupons. Thus, the use of CMCS in EOR should take into the consideration of microbial degradation and its impact on MIC.

Effect of yeast extract supplementation on halotolerant biosurfactant production kinetics coupled with degradation of petroleum crude oil by Acinetobacter baumannii OCB1 in marine environment

The pressing priority is to uncover environmentally secure techniques for abolition of oil spills suited to Indian marine conditions as increase in fuel consumption and demand has resulted in enhanced petroleum crude oil (PCO) transfer via sea route. Acinetobacter baumannii OCB1, isolated from petroleum refinery effluent, when grown in sea water supplemented with PCO (1.0% v/v) and glucose (1.0 g/L) yielded high degradation of C8 hydrocarbons (69.69%). On adding yeast extract (0.05 g/L) it degraded C8–C14 hydrocarbons (3.55–17.48%). Degradation was facilitated by lipopeptide biosurfactant (BS) having needle like surface as depicted by LCMS and FESEM analysis. Yield was higher in presence of yeast extract while there was no significant difference in activity. BS showed excellent stability at wide range of pH, temperature, salinity and high emulsification of petroleum-based oils. BS production modelled by Leudeking Piret model was growth associated and mixed growth associated without and with yeast extract respectively.

Enrichment of f/2 medium hyperaccumulates biomass and bioactive compounds in the diatom Phaeodactylum tricornutum

Photosynthetic microalgae have garnered research attention due to their inherent advantageous characteristics, however, commercial exploitation of algae is still hampered by their relatively compromised overall productivity. Thus, it is of paramount significance to design a strategy to concurrently enhance the growth rate and compounds production. In this study, we interrogated the impact of fortifying bacterial growth medium components in the conventional f/2-medium for microalgae. Our results showed that supplement of yeast extract and tryptone significantly increased cell growth of the model diatom Phaeodactylum tricornutum. Particularly, cell biomass and triacylglyceride content increased up to 3.48-fold and 2.13-fold in the stationary phase, respectively. Besides, fucoxanthin content increased by 1.7-fold. Transcript abundance of key genes involved in carotenoid synthesis also increased significantly. Overall, the results exemplified a feasible and promising strategy to simultaneously enhance the biomass and accumulation of triacylglyceride and fucoxanthin for industrial applications of microalgae.

Oil-lipids, carotenoids and fatty acids simultaneous production by Rhodotorula mucilaginosa CCT3892 using sugarcane molasses as carbon source

Abstract One of the most important classes of nutritional biomolecules is the oleaginous compounds group, which specially includes the oil-lipids, the carotenoids and the fatty acids. These biocompounds present a wide range of industrial applications because their ability to act as an energy source, antioxidants and metabolic agents for the human body. Therefore, the food industry, mainly focusing on food supplementation, is always searching for new sources of them. In this context, the present study evaluated the total lipids, carotenoids and fatty acids simultaneous production by the Rhodotorula mucilaginosa CCT3892 yeast, using residual sugarcane molasses as carbon source. The results obtained demonstrated that the cultivation of yeast in molasses medium (MC) produced the same content of total lipids and carotenoids (16.50% ± 0.68% and 0.053 ± 0.001 mg g-1, respectively) as the obtained from a synthetic medium (SC) (15.36% ± 1.36% and 0.051 ± 0.001 mg g-1 0.005). Concerning the fatty acids biosynthesis, the MC cultivation generated the most interesting profile once it presented a greater content of oleic acid (74.05%), an unsaturated compound with high nutritional value. The cultivation carried out with the molasses and yeast extract supplementation (MYEC) did not provide an improvement in microbial oil production, what indicated that in this condition there was a predominance of others sorts of substrate metabolization by the yeast cells, as confirmed by the microbial kinetics study.

Effect of different sugar sources on P. rhodozyma Y1654 growth and astaxanthin production

Phaffia rhodozyma (also known as Xanthophyllomyces dendrorhous) is one of the most promising natural sources of commercial astaxanthin. It has high growth rates, easy cultivation conditions and able to utilize different carbon substrates. This provides an opportunity to further lower production cost by using industrial waste such as molasses. This research therefore evaluates the growth dynamic and astaxanthin production of P. rhodozyma Y1654 growing on soy and sugar beet molasses-based media. Liquid growth media based on soy molasses (SM), sugar beet molasses (SBM) and glucose (control) as main sugar source with peptone and yeast extract supplementation were inoculated with 48 h old seed culture (grown in standard glucose media: 2.0% glucose, 1.0% peptone, 0.2% yeast extract) and incubated at 20 °C with stirring speed of 180 rpm for 7 days. Samples were taken daily throughout the study period to assess; cell count, dry cell weight (DCW) and amount of astaxanthin. Soy molasses-based media resulted in the highest biomass yield (7.7 g L) followed by SBM (5.8 g L). Generally, more than 90% of initial fermentable sugar was consumed at the end of the study. However, about 40% of total sugar in SM was unassimilable by P. rhodozyma Y1654. The highest astaxanthin yield was observed in the control media (77 µg g of DCW). Cultivation of P. rhodozyma Y1654 in SBM resulted in as much as twice (32.8 µg g of DCW) the astaxanthin yield of SM (12.4 µg g DCW). Molasses-based media are good for growth of P. rhodozyma Y1654 but for astaxanthin production, they need further optimization.

Co‐fermentation of agricultural and industrial waste by Naganishia albida for microbial lipid production in fed‐batch fermentation

AbstractBACKGROUNDOleaginous yeast Naganishia albida is well known for its ability to utilize a variety of carbon sources, including lignocellulosic hydrolysates, complex sugars and fatty acids. In this study, crude glycerol derived from the biodiesel industry and onion waste hydrolysate (OWH) were used as potential substrates for microbial lipid production.RESULTSBoth substrates provided sufficient nutrition to support cell growth and lipid production as sole carbon source. Enhanced lipid production and cell growth rate were observed with supplementation of yeast extract as nitrogen source. Co‐fermentation of OWH and crude glycerol led to improved biomass as well as lipid production. The highest lipid content of 34.0% (w/w) with 21.1 g L−1 of dry cell weight was obtained after 168 h of fed‐batch fermentation with intermittent feeding of crude glycerol and OWH. The lipid concentration was approximately 7 times higher than using mineral medium with crude glycerol as sole carbon source, where a lipid content of 12.6% (w/w) and a maximum biomass of 8.32 g L−1 were obtained at 168 h.CONCLUSIONOptimization of glycerol and OWH feeding could enhance lipid accumulation in N. albida. This study suggests that the co‐fermentation of agricultural and industrial waste as substrates can provide a competitive route for single cell oil production. © 2019 Society of Chemical Industry

Improvement of Bioethanol Production from Sweet Sorghum Juice under Very High Gravity Fermentation: Effect of Nitrogen, Osmoprotectant, and Aeration

To improve ethanol production fermentation efficiency from sweet sorghum juice under a very high gravity (VHG, 280 g/L of total sugar) condition by Saccharomyces cerevisiae NP01, dried spent yeast (DSY), yeast extract, and glycine concentrations were optimized using an L9 (34) orthogonal array design. The results showed that the order of influence on the ethanol concentration (PE) was yeast extract &gt; glycine &gt; DSY. The optimal nutrient concentrations for ethanol production were determined as follows: yeast extract, 3; DSY, 4; and glycine, 5 g/L. When a verification experiment under the projected optimal conditions was done, the P, ethanol yield (Yp/s), and ethanol productivity (Qp) values were 120.1 g/L, 0.47, and 2.50 g/L·h, respectively. These values were similar to those of the positive control experiment with yeast extract supplementation at 9 g/L. The yeast viability under the optimal condition was higher than that of the control experiment. To improve sugar utilization and ethanol production, aeration at 2.5 vvm for 4 h was applied under the optimal nutrient supplementation. The P, Yp/s, and Qp values were significantly increased to 134.3 g/L, 0.50, and 2.80 g/L·h, respectively.

Dimorphism of Trichosporon cutaneum and impact on its lipid production

BackgroundCompared to the oleaginous yeast Yarrowia lipolytica, Trichosporon cutaneum can metabolize pentose sugars more efficiently, and in the meantime is more tolerant to inhibitors, which is suitable for lipid production from lignocellulosic biomass. However, this species experiences dimorphic transition between yeast-form cells and hyphae during submerged fermentation, which consequently affects the rheology and mass transfer performance of the fermentation broth and its lipid production.ResultsThe strain T. cutaneum B3 was cultured with medium composed of yeast extract, glucose and basic minerals. The experimental results indicated that yeast-form morphology was developed when yeast extract was supplemented at 1 g/L, but hyphae were observed when yeast extract supplementation was increased to 3 g/L and 5 g/L, respectively. We speculated that difference in nitrogen supply to the medium might be a major reason for the dimorphic transition, which was confirmed by the culture with media supplemented with yeast extract at 1 g/L and urea at 0.5 g/L and 1.0 g/L to maintain total nitrogen at same levels as that detected in the media with yeast extract supplemented at 3 g/L and 5 g/L. The morphological change of T. cutaneum B3 affected not only the content of intracellular lipids but also their composition, due to its impact on the rheology and oxygen mass transfer performance of the fermentation broth, and more lipids with less polyunsaturated fatty acids such as linoleic acid (C18:2) were produced by the yeast-form cells. When T. cutaneum B3 was cultured at an aeration rate of 1.5 vvm for 72 h with the medium composed of 60 g/L glucose, 3 g/L yeast extract and basic minerals, 27.1 g (dry cell weight)/L biomass was accumulated with the lipid content of 46.2%, and lipid productivity and yield were calculated to be 0.174 g/L/h and 0.21 g/g, respectively. Comparative transcriptomics analysis identified differently expressed genes for sugar metabolism and lipid synthesis as well as signal transduction for the dimorphic transition of T. cutaneum B3.ConclusionsAssimilable nitrogen was validated as one of the major reasons for the dimorphic transition between yeast-form morphology and hyphae with T. cutaneum, and the yeast-form morphology was more suitable for lipid production at high content with less polyunsaturated fatty acids as feedstock for biodiesel production.

Supplementation of Yeast Extract to Practical Diet Improves the Growth, Anti-Oxidative Capacity and Intestinal Morphology of Shrimp Litopenaeus vannamei

Two control diets based on the commercial formula were designed to contain high (27%, D1) and low (22%, D2) levels of fish meal, respectively. Into D2, 500, 1000 and 1500 mg kg−1 of yeast extract were added, respectively, yielding three experimental diets (YE1 through YE3). Shrimp (initial body weight 0.30 g ± 0.02 g) were fed with the experimental diets, five tanks each diet and 30 shrimp individuals each tank, for 8 weeks, and then challenged with Vibrio parahaemolyticus. The results showed that the specific growth rate (SGR) of shrimp in D2 was significantly lower than that of shrimp in D1 (P 0.05). YE significantly improved the activity of glutathione S-transferase. The concentration of glutathione (GSH) and the total serum anti-oxidative capacity (T-AOC) of D1 were significantly higher than those of shrimp feeding other diets (P 0.05). In conclusion, 1000–1500 mg kg−1 of YE was suggested to be supplemented into the practical diets to improve the growth, anti-oxidative capacity and intestinal morphology of shrimp L. vannamei.

Biological diversity of carbon assimilation among isolates of the yeast Dekkera bruxellensis from wine and fuel-ethanol industrial processes.

Dekkera bruxellensis is considered a spoilage yeast in winemaking, brewing and fuel-ethanol production. However, there is growing evidence in the literature of its biotechnological potential. In this work, we surveyed 29 D. bruxellensis isolates from three countries and two different industrial origins (winemaking and fuel-ethanol production) for the metabolization of industrially relevant sugars. The isolates were characterized by the determination of their maximum specific growth rates, and by testing their ability to grow in the presence of 2-deoxy-d-glucose and antimycin A. Great diversity was observed among the isolates, with fuel-ethanol isolates showing overall higher specific growth rates than wine isolates. Preferences for galactose (three wine isolates) and for cellobiose or lactose (some fuel-ethanol isolates) were observed. Fuel-ethanol isolates were less sensitive than wine isolates to glucose catabolite repression (GCR) induction by 2-deoxy-d-glucose. In strictly anaerobic conditions, isolates selected for having high aerobic growth rates were able to ferment glucose, sucrose and cellobiose at fairly high rates without supplementation of casamino acids or yeast extract in the culture medium. The phenotypic diversity found among wine and fuel-ethanol isolates suggests adaptation to these environments. A possible application of some of the GCR-insensitive, fast-growing isolates in industrial processes requiring co-assimilation of different sugars is considered.

Effects of Dietary Yeast Extract Levels on Growth Performance, Digestibility and Antioxidant Capacity of the Taiwan Loach

An 8-week feeding trial was conducted to determine the effects of different levels of dietary Yeast Extract (YE) on growth performance, digestibility and antioxidant capacity of the Taiwan loach. The trial contained 6 diets with different levels of wet YE, namely 0%, 1%, 2%, 3%, 4% and 5% (groups T1-T6). Each group contained 8 replicates with 12 loaches. Results indicated that the Specific Growth Rate (SGR) of loaches that were fed T5 diet were significantly higher than those of the other groups, whereas the feeding rate and feed conversion rate were just the opposite. The association of the regression analysis between different dietary YE and the loach SGR were: SGR=−9244YE3+622.03YE2-3.7768YE+3.9325(p<0.05). The apparent digestibility coefficient of the dry matter and the Amylase activity levels of the loaches fed with the YE were higher than those that were fed the T1 diet. The liver SOD activity was increased significantly following the increase in the YE supplementation (p<0.05). In conclusion, YE supplementation in the loach diet could promote growth, improve feed digestion and utilization, and enhance antioxidant capacity. The optimum levels of wet YE required for feeding the Taiwan loach species were estimated to 4.16%.

Effects of dietary yeast extract supplementation on growth, body composition, non-specific immunity, and antioxidant status of Chinese mitten crab (Eriocheir sinensis)

This study was conducted to evaluate the effects of dietary supplementation with yeast extract on growth, body composition, non-specific immunity, and antioxidant status of Chinese mitten crab (Eriocheir sinensis). A total of 432 crabs (initial average weight, 4.62 ± 0.11 g) were randomly distributed into four treatment groups with six replicates of 18 crabs. The crabs were fed a basal diet or the same diet supplemented with 2.5, 5, and 10 g/kg yeast extract for 8 weeks. The results showed that dietary yeast extract inclusion enhanced the edible viscera index (linear, P < 0.001), edible viscera crude protein (CP) content (linear, P = 0.025) and serum phenoloxidase (ProPO) activity (quadratic, P = 0.023) at 56 day, increased the total superoxide dismutase (T-SOD) activity at 28 day (quadratic, P = 0.037) and catelase (CAT) activity at 56 day (quadratic, P = 0.034) of edible viscera, and muscular T-SOD activity (quadratic, P = 0.020) at 56 day in Chinese mitten crab. Compared with the control group, the inclusion of 5 g/kg yeast extract in the diet increased the edible viscera index, enhanced the CAT activity of edible viscera at 56 day in Chinese mitten crab (P < 0.05). Dietary 10 g/kg yeast extract inclusion enhanced the edible viscera index at 56 day in Chinese mitten crab than that of the control group (P < 0.05). These results implied that dietary yeast extract inclusion improved the edible viscera index and crude protein content of edible viscera, enhanced serum immunity, and increased the antioxidant status of edible viscera and muscle in Chinese mitten crab, especially when it is supplemented at 5 g/kg yeast extract in the diet.

Low Carbon Concentration Feeding Improves Medium-Chain-Length Polyhydroxyalkanoate Production in Escherichia coli Strains With Defective β-Oxidation

Medium-chain-length (MCL) polyhydroxyalkanoates (PHAs) of near homopolymeric composition are unnatural polymers, having almost identical repeating units throughout the polymer chain. These homopolymeric PHAs can be produced by β-oxidation defective bacterial hosts. Escherichia coli is an attractive workhorse for the production of such genetically engineered PHAs; however, achieving efficient production of the near homopolymers by β-oxidation defective strains is a major challenge because of a lack of process development studies. In order to address this issue, we investigated the optimization of carbon feeding for efficient production of MCL-PHAs by an E. coli strain with defective β-oxidation, LSBJ. Engineered bacteria were cultured in shake-flasks with intermittent feeding of a fatty acid substrate [either decanoate (C10) or dodecanoate (C12)] at various concentrations together with a co-carbon source (glucose, glycerol, or xylose) in order to support cell growth. It was found that feeding low concentrations of both fatty acids and co-carbon sources led to an enhanced production of MCL-PHAs. Additionally, the supplementation of yeast extract improved cell growth, resulting in achieving higher titers of MCL-PHA. As a result, poly(3-hydroxydecanoate) [P(3HD)] and poly(3-hydroxydodecanoate) [P(3HDD)] were produced up to 5.44 g/L and 3.50 g/L, respectively, as near homopolymers by employing the developed feeding strategy. To the best of our knowledge, we record the highest titer of P(3HD) ever reported so far.

Cumulative effect of yeast extract and fructooligosaccharide supplementation on composition and metabolic activity of elderly colonic microbiota in vitro

Concurrent with a decline in general health, elderly gut microbiota is characterized by reduced stability compared to adults, and is impacted by living condition and diet. Dietary supplementation was suggested to stabilize and promote elderly gut microbiota. We used two PolyFermS models to investigate the impact of fructooligosaccharides (FOS), nucleosides (NS), and yeast extract (YE) supplementation on elderly colonic microbiota in vitro. NS, YE and FOS tested separately and combined at different addition levels increased the abundance of butyrate producers, lactobacilli and bifidobacteria. FOS and YE cumulatively increased butyrate levels, while propionate productions were decreased. Gene expression analysis indicated that FOS enhanced abundance of transcripts related to ‘Di-and Oligosaccharides’ and ‘Fermentation’ while treatments with FOS and YE alone and in combination altered the transcriptional profile of ‘Amino Acids and Derivatives’.Our findings suggest that YE rich in nucleotides, amino acids, vitamins and minerals, enhance the butyrogenic effect of FOS.