Abstract
The coproduction of glucan and mannan from yeast extract residue was examined by clarifying the material balance and energy consumption at the factory scale. As final products, yeast glucan and yeast mannan with purities of 46.2% and 50.9% were obtained at 92.6% and 65.9% yields, respectively. This result demonstrated that glucan and mannan can be produced simultaneously using the existing equipment at the yeast extract factory. Losses of glucan and mannan were mainly generated in the separation process at 5.4% and 29.1%, respectively. The energy in the total process per ton of raw material (yeast extract residue) containing 85.0% water by weight required 122 kWh of electricity, 1.54 t of steam (0.68 MPa, 174.5 °C), and 11.0 kg of liquid natural gas. The material balance revealed a quantitative relationship between purity and yield in the coproduction that will help optimize yeast-derived glucan and mannan production in the future.
Introduction
Brewer's spent yeast is generated at 20–40 wet-kg per 1 kL of beer production (Fărcaş et al., 2017) and reused as a raw material for dried yeast and extracts worldwide (Chae et al., 2001). Yeast extracts are the soluble components inside yeast cells that have been separated after partial degradation of the yeast cell wall (YCW) by endogenous or exogenous enzymes (Tangler and Erten, 2008; Chae et al., 2001). They are mainly used as a flavor enhancer (Vieira et al., 2013). During the yeast extract production, yeast extract residue (YER) containing YCW as the main component is generated as a by-product in the amount of 50–60% of the weight of the spent yeast (Suphantharika et al., 1997). Until the enforcement of the 1996 Protocol to the London Convention, which prohibits the ocean disposal of wastes, YER was generally dumped into the ocean, but is now mainly used as livestock feed after drying as an ecofeed (Borchani et al., 2014). Furthermore, extracting and effectively using the two main components of YER, yeast β-glucan (YG) and yeast α-mannan (YM), is also considered to improve YER's added value.
YG and YM are indigestible polysaccharides that constitute YCW. YG has been reported to have the potential to be used in a wide range of applications such as livestock immunostimulant (Thanardkit et al., 2002), thickener (Raikos et al., 2018), fat replacer (Worrasinchai et al., 2006), and antidiabetic drugs (Cao et al., 2017). Moreover, YG has already been commercially available as a feed additive and supplement for pets or humans. On the other hand, YM is also expected to be used as emulsifiers (da Silva Araújo et al., 2014; de Melo et al., 2015), prebiotics (Oba et al., 2020; Tanihiro et al., 2020), and medical ingredients (Lew et al., 2017; Jin et al., 2019). YM is already commercially available as a feed additive and wine stabilizer.
A method for YG production (Magnani et al., 2009) has been reported to recover insoluble YG after solubilizing YER proteins and mannan using alkaline extraction at high temperatures (0.25–1 mol/L NaOH at 90 °C for 2–9 h; Varelas et al., 2015; Long et al., 2019) or protease (Freimund et al., 2003). Similarly, a method for YM production has been reported to recover mannan solubilized by alkaline extraction at high temperatures (0.25–0.5 mol/L NaOH at 90–100 °C for 2–5 h; Liu et al., 2015; Maru et al., 2015; Li and Karboune, 2018) or β-1,3 glucanase (da Silva Araújo et al., 2014). In other words, conventional YG and YM are manufactured based on the same principle, i.e., the mannan in YER is solubilized using alkali or enzyme extraction methods and separated from the insoluble glucan.
A combined production process that recovers YG and YM simultaneously is theoretically possible. However, conventional manufacturing methods have adopted a way of imposing impurities (e.g., protein, lipid, ash) on the by-product side to recover only YG or YM as a high-purity main product. Although YG or YM can be recovered from the by-products using the conventional method, it can become more effective to collect YG or YM from raw materials than from the by-products because inefficient purification is not required.
From the perspective of the circular economy, it will be necessary to make the best use of YER. In other words, it is essential to increase the overall yield of YG and YM by recovering both from the YER. In general, increasing the yield of YG and YM is expected to reduce the purity of both products. Therefore, if the purity required for the final products is lowered, theoretically, two products could be produced in higher yield in a YG/YM combined production system. In addition, low-purity YG and YM (e.g., 40–50%) also have the potentials to be commercially used (Immunostimulant YG: Thanardkit et al., 2002; Prebiotic YM: Oba et al., 2020).
While many studies have reported that high-purity YG or YM was obtained, there are only lab-scale reports on the YG/YM production (da Silva Araújo et al., 2014; Sedmak, 2014; Yu et al., 2014). Moreover, no quantitative report has been made on the relationship between purity and yield in the YG or YM production. Although it is essential to clarify the material balance for the practical application and optimization of the process (Dammak et al., 2014), the material balance of YG and YM production has not been reported.
This study aims to demonstrate the coproduction of YG and YM from YER at an actual yeast extract manufacturing factory and clarify the material balance, energy consumption, purity, and yield. In this demonstration, the existing equipment in the yeast extract manufacturing factory, for example, tanks and centrifuges, was diverted to manufacturing YG and YM with the aim of simplification of a retrofitted design for existing processes. Finally, based on the material balance results, the possibility of further efficiency improvement and practical application will be discussed.
Materials and Methods
Raw material The YER after extraction treatment from brewer's spent yeast (Saccharomyces pastorianus) was used as the raw material. YER was obtained as a by-product by autolyzing the brewer's spent yeast under acid conditions overnight using previously reported methods (Tammakiti et al., 2004; Tanguler and Erten, 2008) and removing the yeast extract using a centrifuge. The YER was in the form of a slurry containing 85.0% water by weight. Table 1 shows the dry matter composition of the YER under test.
Table 1.
The composition of YER.
| Compositions [g/100 g-dry YER] |
| Glucan |
Mannan |
Protein |
Lipid |
Ash |
Others |
| 28.9 |
20.0 |
33.5 |
7.2 |
3.8 |
6.6 |
Coproduction of YG and YM Coproduction of YG and YM was performed as described previously (Ishida et al., 2012; Minami et al., 2020) by diverting the actual yeast extract production equipment in a food factory. The targeted purity of YG and YM as final products was set at 40–50% based on the commercial use potential of low-purity products, as cited in the Introduction chapter. The alkaline extraction method with the weaker condition than the conventional method was selected as a new improvement to avoid excessively solubilizing impurities and remaining salts in the soluble fraction. The process flow is shown in Fig. 1. The coproduction process consists of the following four steps: (1) YER washing, (2) alkaline extraction and pH adjustment, (3) separation of YG and YM, and (4) concentration, sterilization, and drying.
The YER slurry was weighed in the load cell of an extraction tank and used as a raw material. First, the soluble extract component remaining in YER was removed by a centrifuge with the addition of water and NaOH to adjust to pH 10–11. After washing, the YER was heated using a plate heat exchanger, and sent to the extraction tank. The proteins and YM in the YER were solubilized in an extraction tank under weak alkaline conditions at 80 ± 10 °C, overnight with stirring. The YER after alkaline extraction was neutralized and adjusted to pH = 6 ± 1 with pH adjuster (organic acid), and then centrifuged with the addition of water and separated into a heavy insoluble fraction containing YG and a light soluble fraction containing YM.
The YM fraction was concentrated in an evaporator and then sterilized in a heat sterilizer at 125 °C for 40 s. The sterilized YM concentrate was dried by a spray dryer to become a powdery crude YM product. The YG fraction was not sterilized and dried in the demonstration. The mass balance and energy consumption in sterilization and drying of the YG fraction were calculated based on similar operations data at the plant, assuming that the YG fraction was sterilized at 125 °C for 40 s and dried with a drum dryer until water content reached 5%.
Material balance The entire process's material balance was investigated for water and solids components, such as glucan, mannan, protein, lipid, and ash. The weights of raw materials, intermediate products, and final products were measured in each tank's load cells. The weight of water added directly to the pipe and the liquid discharged from the pipe or centrifuge were calculated by multiplying the flow rate measured with flow meters, the addition/discharge time, and the density. The liquid sample density was measured at 20 °C using a density hydrometer DA-250 (Kyoto Electronics Manufacturing Co., Ltd., Kyoto, Japan). The amount of chemicals input was calculated by measuring the chemical tank's weight before and after the addition with a weighing scale. Ingredient composition was calculated by multiplying each component analysis value per dry matter by the samples' solids content.
Utility consumption The types of utilities used in the processes were first investigated. The consumption of utilities such as electricity, steam (0.68 MPa, 174.5 °C), and fuel (liquid natural gas [LNG]) required for coproduction of YG and YM was calculated by multiplying by the operating time or processing volume in this demonstration by the unit data collected from each facility in the factory.
Yields calculation The yields of YG and YM in the process were calculated by dividing the amount of glucan and mannan recovered as a final product by the amount of glucan and mannan in YER, respectively, and expressed as a weight percentage.
Glucan and mannan analysis The contents of glucan and mannan in the dried sample were determined by the sulfuric acid hydrolysis method described by Shirai and Yoshida (2020). As a pretreatment, the samples were hydrolyzed at 121 °C for 1 h by adding 12 mol/L sulfuric acid and deionized water until the sulfuric acid concentration reached 0.45 mol/L. The hydrolyzed sample was neutralized with 19 mol/L NaOH, filtered, and then subjected to high-performance liquid chromatography (HPLC; LC-10AD; Shimadzu Corp., Kyoto, Japan) fitted with a fluorescence detector. The glucose and mannose derived from glucan and mannan were separated on a TSKgel SUGAR AX I column (Tosoh Corp., Tokyo, Japan) using 0.5 mol/L of borate buffer as the mobile phase at a flow rate of 0.7 mL/min. The column temperature was maintained at 60 °C. Glucose and mannose were detected using the fluorescence detector with a set excitation wavelength of 320 nm and measurement wavelength of 430 nm. The glucan and mannan concentrations in the samples were calculated by multiplying the HPLC analysis values by 0.9 as derived from the following quantitative relationships: molecular weight of monomer of polysaccharides (162)/molecular weight of monosaccharides (180).
Analysis of other components The samples' water content was determined by the oven method drying at 105°C for 5 h. The sample's total solid concentration was calculated by subtracting the sample's water content from 100%. The protein content was calculated by multiplying the total nitrogen concentration measured by the Kjeldahl method by 6.25 as the nitrogen-protein conversion factor (AOAC official method, 984.13). Lipids were quantified by the acid hydrolysis method (AOAC official method, 925.12). The ash content was determined by the gravimetric method, in which the samples were incinerated at 550 °C to a constant weight.
Results and Discussion
Total material balance Fig. 2 shows the total material balance of coproduction of YG and YM from YER. Overall, YG and YM as final crude products were obtained with 82.2 kg and 37.7 kg in dry matter, respectively, from a ton of YER (150 kg-dry matter). Table 2 compares the purity and yield results in this study with previous studies. As final crude products, the yields of YG with a glucan purity of 46.2% and YM with a mannan purity of 50.9% were 92.6% and 65.9%, respectively. This result indicates that YG and YM coproduction is possible from the manufacturing procedure at a factory scale.
Table 2.
Purity and yield in the demonstration comparing to the previous studies.
Asterisks (*) represent the YG or YM yields, which were calculated by dividing the amount of glucan or mannan recovered as a final product by the amount of glucan or mannan in the spent yeast.
As auxiliary materials per ton of YER in this process, 4.1 t of water, 2.3 kg of NaOH as 100% concentration, and 2.1 kg of pH adjuster (organic acid) as 100% concentration were used. As by-products or wastes, 2.9 t of wastewater and 2.1 t of distilled water per ton of YER were generated. This process was found to consume a large amount of water, although it requires a lower amount of chemicals. In particular, the amount of water used in YER washing occupied 70.3% of total water consumption. The YER washing step aims to improve YM's purity by washing away the soluble yeast extract remaining in YER and preventing the transfer of yeast extract components to the soluble fraction after alkaline extraction. Therefore, if YM's target purity is set even lower, it is possible to eliminate the YER washing step that consumes a great amount of water.
However, it is essential to determine whether the wastewater generated in coproduction can be treated by the yeast extract factory's existing wastewater treatment facility. The 2.9 tons of wastewater generated from 1 ton of YER washing in this demonstration had a solid content concentration of 1.1% and the wastewater load of approximately 20 g of chemical oxygen demand (COD) per liter. The wastewater in this demonstration could be treated sufficiently by the anaerobic wastewater treatment of the existing yeast extract factory (data not shown).
Energy consumption Table 3 shows the energy consumption of the coproduction of YG and YM. The drying process's electricity consumption was 79.0 kWh per ton of YER, equivalent to 64.8% of the total electricity consumption. LNG was used in the spray-drying process and consumed 11.0 kg per ton of YER. Steam was mainly consumed in the YM fraction concentration process and the YG fraction drum dry process, equivalent to 27.5% and 62.7% of the entire process's total steam consumption.
Table 3.
Energy consumption of coproduction of YG and YM.
|
Units of operation |
Energy consumption (per a ton of YER) |
|
Electricity |
Steam |
LNG |
|
|
[kWh] |
[kg] |
[kg] |
| (1) |
YER slurry washing/ heating |
12.9 |
146.8 |
- |
| (2) |
Alkaline extraction/ pH adjustment |
8.1 |
- |
- |
| (3) |
YG/YM separation |
14.6 |
- |
- |
| (4) |
YG sterilization/ drying |
50.0 |
969.2 |
- |
|
YM concentration |
7.3 |
425.5 |
- |
|
YM sterilization/ drying |
29.0 |
3.3 |
11.0 |
|
Total |
121.9 |
1544.8 |
11.0 |
As a measure to reduce energy consumption, it is effective to reduce the amount of evaporated water in the concentration and drying process, which consumed a large amount of energy. In the case of diverting the existing yeast extract equipment as in this demonstration, the energy efficiency and concentration rate cannot be changed. However, it may be energy-effective to set a high ratio of solids in washing and alkaline extraction to reduce the amount of evaporated water. Besides, the washing process's electricity consumption can be saved by reducing the amount of washing water although the energy-saving effect is small. However, it is necessary to pay attention to the trade-off between the saving energy and the decrease in purity by reducing the amount of water for washing.
Material balance for glucan As shown in Fig. 2, from the viewpoint of YG production, the glucan loss was 7.4% in the entire process, as calculated with the ratio of the glucan amount (40.0 kg) in crude YG products to the glucan amount (43.2 kg) in the YER, which showed a 2% and 5.4% loss in the YER washing and separation processes, respectively. The glucan purity of the YG products obtained in this study (46.3%) was lower than the glucan purity (54.6–91.8%) reported in many previous reports (Table 2). The reason for this finding is that the previous studies have set process goals that prioritize purity. In addition, the purity of glucan in YER as the raw material used in this study was about 5–10% lower than in previous studies (Thanardkit et al., 2002), which may have affected the decrease in glucan purity.
The main impurities of crude YG products were protein, lipid, and mannan at 19.8%, 10.9%, and 10.1%, respectively. Compared with the alkaline extraction conditions for YER in previous studies (0.25–1 mol/L NaOH, 90 °C, 2–9 h: Varelas et al., 2015; Long et al., 2019), this study's condition was weaker, although the reaction time was longer (< 0.1 mol/L NaOH, 80 ± 10 °C, overnight). The mitigation of the alkaline extraction conditions was considered to have suppressed the progress of solubilization of proteins and mannoproteins in YCW. As a result, the proteins, lipids, and mannan in the YCW remained in the insoluble crude YG. Conversely, improving the glucan purity of YG in the coproduction process requires higher alkaline concentrations and temperatures or the use of additional enzymes, such as mannanase and protease, to solubilize the mannan component of YCW further, as suggested in previous studies (Varelas et al., 2015; Yu et al., 2014). This approach can also be expected to improve the mannan yield of YM. To reduce proteins and lipids in YG, solubilization of proteins in the YCW by acid extraction (Shokri et al., 2008) and lipid solubilization by lipase treatment (Borchani et al., 2014) are also useful. Acid extraction and enzyme treatment can be conducted in the existing tanks; therefore, additional capital investment is not needed, but equipment occupancy time, utility consumption, and by-product generation would increase.
Material balance for mannan From the viewpoint of YM production (Fig. 2), the mannan loss was 34.1% for the entire process, calculated with the ratio of the mannan amount (19.7 kg) in crude YM products to the mannan amount (29.9 kg) in the YER, of which 5.0% and 29.1% were obtained in the YER washing and separation processes. The mannan purity of the YM products obtained in this study (50.9%) was equivalent to that of YM used as a new prebiotic material reported by Oba et al. (2020) (50.5%), although it was lower than the mannan purity reported previously (Table 2).
The mannan loss in the separation process was considered mainly due to the presence of mannan that was not partially solubilized in the alkaline extraction process. As mentioned earlier, the mannan yield as YM can be improved by setting a high alkaline concentration or using an additional enzyme. However, especially when changing the condition of alkaline extraction, it is necessary to pay attention to the effect on YM's mannan purity because there are risks such as solubilization of impurities and an increase in salt due to pH adjustment.
The main impurities contained in YM were protein (23.8%), glucan (5.9%), ash (4.9%), and other components (10.6%). Approximately half of the other components are assumed to be derived from the organic acid used for pH adjustment (Fig. 2). As a further method for purifying YM, there is an option of adding ethanol precipitation and protease treatment. However, the ethanol precipitation method as commonly practiced at the lab scale is not an applicable process for the factory scale because it requires a large amount of organic solvent. The protease treatment process is possible as an industrial process by combining it with separation using ion-exchange membranes and microfiltration, but additional capital investment and operating costs are required. Furthermore, additional studies such as appropriate enzyme treatment conditions and membrane selection are also essential.
Coproduction of YG and YM from YER In the industrial coproduction of YG and YM from YER, there is a concern that the quality and yield of products may fluctuate due to variations in the composition of the raw material. It is naturally desirable that the quality of YER as raw material is stable. However, it has been reported that the composition of YCW, which is the main component of YER, differs depending on the yeast species, culture conditions (e.g., medium, pH, temperature), and extraction method (Aguilar-Uscanga and François, 2003). Therefore, in food factories that produce yeast extract from various yeasts, it is necessary to consider measures to stabilize the quality of YER as a by-product. For example, the YER washing process proposed in this study effectively reduces variations in the quality of the raw materials. From the viewpoint of maintaining the quality of the products, it is relatively realistic to set product standards that allow a specific range of quality variations in the glucan or mannan content. Also, the blend of a lot at lower YG/YM purity than the product standard with another lot at higher YG/YM purity can be a practical measure to realize stable production. In the future, a series of value chains, such as beer brewing, baking, manufacturing yeast extracts, and coproducing YM and YG should work together to optimize as a single system while being aware of downstream processes to achieve stable production for the entire industry.
The commercial value of low-purity YG and YM obtained in this study was evaluated. The purity of YG obtained in this study (46.2%) was within the range of glucan purity commercially used products (immunostimulant: 42.5–52.0%, thickener: 42.5%, Thanardkit et al., 2002). The purity of YM obtained in this study (50.9%) was similar to that of prebiotic mannan for commercial use (50.5%: Oba et al., 2020). Therefore, the low-purity YG and YM obtained in the combined production system of this study can be used commercially, although the actual functional evaluation has not been verified.
Conclusion
This study clarified the material balances and energy consumption in detail for the coproduction of YG and YM from the YER at a factory scale. As a result, glucan and mannan with purities of 46.2% and 50.9% could be recovered in 92.6% and 65.9% yields, respectively. This result indicates that glucan and mannan can be produced simultaneously by setting a relatively low alkaline condition. The process was demonstrated using the yeast extract factory's existing equipment without making an additional capital investment. The losses of glucan and mannan were mainly generated in the separation process after alkaline extraction. Most of the energy in this coproduction system was consumed in the drying process. The material balance revealed a quantitative relationship between purity and yield in the coproduction of YG and YM. This finding will help to optimize yeast-derived glucan and mannan production in the future.
Acknowledgements The authors are grateful to Asahi Group Foods Co., Ltd. for providing the raw material and lending manufacturing equipment. We also thank Dr. Ueno (Asahi Group Foods Co., Ltd.) and Dr. Minami (Asahi Group Foods Co., Ltd.) for useful discussions. Activities of the Presidential Endowed Chair for “Platinum Society” in the University of Tokyo are supported by the KAITEKI Institute Incorporated, Mitsui Fudosan Corporation, Shin-Etsu Chemical Co., ORIX Corporation, Sekisui House, Ltd., the East Japan Railway Company, and Toyota Tsusho Corporation.
Conflict of interest There are no conflicts of interest to declare.
References
- Aguilar-Uscanga, B. and François, J.M. (2003). A study of the yeast cell wall composition and structure in response to growth conditions and mode of cultivation. Lett. Appl. Microbiol., 37, 268-274.
- Borchani, C., Fonteyn, F., Jamin, G., Paquot, M., Blecker, C., and Thonart, P. (2014). Enzymatic process for the fractionation of baker's yeast cell wall (Saccharomyces cerevisiae). Food Chem., 163, 108-113.
- Cao, Y., Sun, Y., Zou, S., Li, M., and Xu, X. (2017). Orally administered baker's yeast β-glucan promotes glucose and lipid homeostasis in the livers of obesity and diabetes model mice. J. Agric. Food Chem., 65, 9665-9674.
- Chae, H.J., Joo, H., and In M.J. (2001). Utilization of brewer's yeast cells for the production of food-grade yeast extract. Part 1: effects of different enzymatic treatments on solid and protein recovery and flavor characteristics. Bioresour. Technol., 76, 253-258.
- Dammak, I., Neves, M., Souilem, S., Isoda, H., Sayadi, S., and Nakajima, M. (2014). Material balance of olive components in virgin olive oil extraction processing, Food Sci. Technol. Res., 21, 193-205.
- da Silva Araújo, V.B., de Melo, A.N.F., Costa, A.G., Castro-Gomez, R.H., Madruga, M.S., de Souza, E.L., and Magnani, M. (2014). Followed extraction of β-glucan and mannoprotein from spent brewer's yeast (Saccharomyces uvarum) and application of the obtained mannoprotein as a stabilizer in mayonnaise. Innov. Food Sci. Emerg. Technol., 23, 164-170.
- de Melo, A.N.F., de Souza, E.L., da Silva Araújo, V.B., and Magnani, M. (2015). Stability, nutritional and sensory characteristics of French salad dressing made with mannoprotein from spent brewer's yeast. LWT-Food Sci. Technol., 62, 771-774.
- Fărcaş, A.C., Socaci, S.A., Mudura, E., Dulf, F.V., Vodnar, D.C., Tofană, M., and Salanţă, L.C. (2017). Exploitation of brewing industry wastes to produce functional ingredients. In “Brewing Technology,” ed. by M. Kanauchi. Intech Open.: London, UK, 137-156.
- Freimund, S., Sauter, M., Käppeli, O., and Dutler, H. (2003). A new non-degrading isolation process for 1,3-β-D-glucan of high purity from baker's yeast Saccharomyces cerevisiae. Carbohydr. Polym., 54, 159-171.
- Ishida, T., Kanaoka, Y., Ohuchi, A., Arai, Y., and Suzuki, K. (2012). Method for producing yeast water-soluble polysaccharide. JP Patent No. 4979924, Jul. 18.
- Jin, X., Zhang, M., Cao, G. F., and Yang, Y. F. (2019). Saccharomyces cerevisiae mannan induces sheep beta- defensin-1 expression via Dectin-2-Syk-p38 pathways in ovine ruminal epithelial cells. Vet. Res., 50, 8.
- Kim, K.S. and Yun, H.S. (2006). Production of soluble β-glucan from the cell wall of Saccharomyces cerevisiae. Enzyme Microb. Technol., 39, 496-500.
- Lew, D.B., Michael, C.F., Overbeck, T., Robinson, W.S., Rohman, E.L., Lehman, J.M., Patel, J.K., Eiseman, B., LeMessurier, K.S., Samarasinghe, A.E., and Gaber, M.W. (2017). Beneficial effects of prebiotic Saccharomyces cerevisiae mannan on allergic asthma mouse models. J. Immunol. Res., 2017, 3432701.
- Li, J. and Karboune, S. (2018). A comparative study for the isolation and characterization of mannoproteins from Saccharomyces cerevisiae yeast cell wall. Int. J. Biol. Macromol., 119, 654-661.
- Liu, H. Z., Liu, L., Hui, H., and Wang, Q. (2015). Structural characterization and antineoplastic activity of Saccharomyces cerevisiae mannoprotein, Int. J. Food Prop., 18, 359-371.
- Long, N. T., Ha, T. L. T., Son, H. N., and Luan, L. Q. (2019). Radiation degradation of β-glucan extracted from brewer's yeast for enhancing growth promotion and immunostimulant activities on broilers. Int. J. Polym. Sci., 2019, 8901824.
- Magnani, M., Calliari, C.M., Macedo Jr., F.C.D., Mori, M.P., Syllos Cólus, I.M.D., and Castro-Gomez, R.J.H. (2009). Optimized methodology for extraction of (1 → 3) (1 → 6)-β-D-glucan from Saccharomyces cerevisiae and in vitro evaluation of the cytotoxicity and genotoxicity of the corresponding carboxymethyl derivative. Carbohydr. Polym., 78, 658-665.
- Maru, V., Hewale, S., Mantri, H., and Ranade, V. (2015). Partial purification and characterization of mannan oligosaccharides from cell wall of Saccharomyces cerevisiae. Int. J. Curr. Microbiol. Appl. Sci., 4, 705-711.
- Minami, T., Imai, Y., Ishida, T., Yoshida, J., and Shirai, T. (2020). Interleukin-6, 10 production promoter. WO Patent No. 2020003905A1, Jan. 2.
- Oba, S., Sunagawa, T., Tanihiro, R., Awashima, K., Sugiyama, H., Odani, T., Nakamura, Y., Kondo, A., Sasaki, D., and Sasaki, K. (2020). Prebiotic effects of yeast mannan, which selectively promotes Bacteroides thetaiotaomicron and Bacteroides ovatus in a human colonic microbiota model. Sci. Rep., 10, 17351.
- Raikos, V., Grant, S.B., Hayes, H., and Ranawana, V. (2018). Use of β-glucan from spent brewer's yeast as a thickener in skimmed yogurt: Physicochemical, textural, and structural properties related to sensory perception. J. Dairy Sci., 101, 5821-5831.
- Sedmak, J. J. (2014). Production of beta-glucans and mannans. US Patent No. 8753668, Jun. 17.
- Shirai, T. and Yoshida, J. (2020). Immunostimulatory agent and method for preventing infection. WO Patent No. 2020075424A1, Apr. 16.
- Shokri, H., Asadi, F., and Khosravi, A. R. (2008). Isolation of β-glucan from the cell wall of Saccharomyces cerevisiae. Nat. Prod. Res., 22, 414-421.
- Suphantharika, M., Varavinit, S., and Shobsngob, S. (1997). Determination of optimum conditions for autolyzed yeast extract production. ASEAN J. Sci. Technol. Dev., 14, 21-28.
- Tammakiti, S., Suphantharika, M., Phaesuwan, T., and Verduyn, C. (2004). Preparation of spent brewer's yeast β-glucans for potential applications in the food industry. Int. J. Food Sci. Technol., 39, 21-29.
- Tanguler, H. and Erten, H. (2008). Utilization of spent brewer's yeast for yeast extract production by autolysis: The effect of temperature. Food Bioprod. Process., 86, 317-321.
- Tanihiro, R., Sakano, K., Oba, S., Nakamura, C., Ohki, K., Hirota, T., Sugiyama, H., Ebihara, S., and Nakamura, Y. (2020). Effects of yeast mannan which promotes beneficial bacteroides on the intestinal environment and skin condition: A randomized, double-blind, placebo-controlled study. Nutrients, 12, 3673.
- Thanardkit, P., Khunrae, P., Suphantharika, M., and Verduyn, C. (2002). Glucan from spent brewer's yeast: preparation, analysis and use as a potential immunostimulant in shrimp feed. World J. Microbiol. Biotechnol., 18, 527-539.
- Varelas, V., Liouni, M., Calokerinos, A.C., and Nerantzis, E.T. (2015). An evaluation study of different methods for the production of β-D-glucan from yeast biomass. Drug Test. Anal., 8, 46-55.
- Vieira, E., Brandão, T., and Ferreira, I.M.P.L.V.O. (2013). Evaluation of brewer's spent yeast to produce flavor enhancer nucleotides: Influence of serial repitching. J. Agric. Food Chem., 61, 8724-8729.
- Worrasinchai, S., Suphantharika, M., Pinjai, S., and Jamnong, P. (2006). β-Glucan prepared from spent brewer's yeast as a fat replacer in mayonnaise, Food Hydrocolloids, 20, 68-78.
- Yu, X., Li, Z., Yu, M., Yao, J., and Zhang, Y. (2014). Method for preparing glucan and mannan, glucan preparation and mannan preparation produced thereby and use thereof. US Patent No. 8679797, Mar. 25.
- Zhu, F., Du, B., and Xu, B. (2016). A critical review on production and industrial applications of beta-glucans. Food Hydrocolloids, 52, 275-288.
