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Modern Solid State Fermentation
Chapters (7)
"Modern Solid State Fermentation: Theory and Practice" covers state-of-the-art studies in the field of solid state fermentation (SSF). In terms of different characteristics of microbial metabolites, this book catalogs SSF into two main parts: anaerobic and aerobic SSF. Based on the principles of porous media and strategies of process control and scale-up, which are introduced in the book, it not only presents a well-founded explanation of essence of solid state fermentation, but also their influence on microbial physiology. In addition, due to the rapid development of this field in recent years, inert support solid state fermentation is also examined in detail. At last, the modern solid state fermentation technology platform is proposed, which will be used in solid biomass bioconversion. This book is intended for biochemists, biotechnologists and process engineers, as well as researchers interested in SSF. © Springer Science+Business Media Dordrecht 2013. All rights are reserved.
As discussed in Chap. 1, solid-state fermentation is an important bioprocess. In this process, microorganisms are the most important participant. Because of the unique characteristics of the solid matrix and the rich interface environment it forms, microorganisms in solid-state fermentation show some different features compared with liquid culture. This chapter mainly discusses the relationship of solid-state fermentation and the solid matrix, the physiological metabolism and growth characteristics of microorganisms in the solid matrix, and the interactions between the microorganisms and the solid matrix. The aseptic techniques and inoculation techniques for large-scale solid-state fermentation are discussed in the last part of this chapter. Note that the dynamics model of fractal dimension established in my laboratory can quantitatively characterize the variation law of morphology with the microbial growth in solid-state fermentation and can be used as indicators for biomass yield in the solid-state fermentation process, which provides a new way to automate process control for solid-state fermentation.
Industrial solid-state fermentation (SSF) is not widely used because of engineering difficulties and the lack of guided principles on the fermentation process and scale-up from the physics aspect and porous medium. From the nature of the biological processes, SSF can be featured as the continuous phase of the gas phase compared with the continuous phase of the liquid phase in submerged fermentation. It is important to recognize traditional SSF from the aspect of the gas-liquid-solid phase. In SSF, mass and heat transfer are crucial for understanding and applying this old technology. This chapter introduces the essence of SSF and its related influencing factors from the engineering aspect. It includes the essence of SSF, transfer principles, thermal physics phenomenon, and design and scale-up of bioreactors. The hope is to find novel means to solve the problems of mass and heat transfer in SSF and eventually achieve its industrialization.
Based on the nature of biological processes, aerobic solid fermentation can be defined as a biological metabolic process that uses air containing oxygen as the continuous phase. In the natural environment, the majority of microorganisms live under aerobic conditions, so aerobic solid fermentation simulates the natural environmental condition, and it may be more suitable for the growth of microorganisms. Current model simulations of different fermentation technologies describe the fermentation transfer principle. Various bioreactors have been designed, investigated, and scaled up. The large-scale industrial application of aerobic solid-state fermentation concludes the production of antibiotics, organic acids, enzymes, biofeeds, biopesticides, edible fungi, and so on. In this chapter, the physical and biological characteristics of aerobic solid fermentation are introduced; the related fermentation technologies and bioreactors are described and discussed, especially gas double dynamic solid-state fermentation.
Anaerobic solid-state fermentation has unique advantages in that it is water and energy saving and provides environmental protection; it will be the future direction of the fermentation industry. Anaerobic solid-state fermentation has shown tremendous application potential in the fermentation industry, agriculture, and treatment of organic solid waste. This chapter first analyzes the biological and physics basis of anaerobic solid-state fermentation. The typical case is reported in more detail, including principles, processes, and trends. The breakthroughs of reactors for production of ethanol and biogas are based on anaerobic solid-state fermentation. Anaerobic solid-state fermentation can be used in to produce such as things as bio-based energy, chemicals, traditional food, and agricultural feed and assist with environmental protection, especially for silage and solid waste treatment.
Despite the potential of solid-state fermentation (SSF) systems, some physical aspects related to heterogeneity and nutrition of the media are serious constraints. To overcome these problems, it is convenient to use supports that have well-characterized properties and a minimum of interaction with the biological process. SSF carried out on inert support materials (adsorbed carrier solid-state fermentation, ACSSF) is proposed based on the principle of SSF and is regarded as a future development for SSF systems. The ACSSF system is composed of porous, heterogeneous, biologically inactive material, called an inert support, in which defined culture media and inoculum are absorbed. Cell growth takes place under controlled aerated conditions within suitable reactors kept at a constant temperature. In this chapter, the properties of inert carriers, the techniques, and fermentors of ACSSF and its process optimization are expatiated. Some typical examples are used to project the future of ACSSF. In addition, the economy and the problems of ACSSF are discussed.
Solid-state fermentation (SSF) has unique water- and energy-saving advantages. Some problems related to it need to be solved before effective industrial production. Theoretical and technical breakthroughs are needed to boost the progress of SSF technology and engineering. In-depth knowledge of the nature of SSF is necessary. Research and application of online monitoring technology are key points in regulation of the SSF process. A new solid-state bioreactor was designed and manufactured to meet the needs of current industrial production. It is important to study optimization of the mixed fermentation process. Multidisciplinary research on basic theory and industrial applications is needed, and breakthroughs in SSF for solution of problems should continue. An overview of biomass bioconversion by SSF and corresponding advances achieved in recent years are discussed, especially progress achieved by our group based on the characteristics of solid biomass.
Conventional sugarcane-to-ethanol conversion occurs via a series of process steps, inter alia, energy-intensive juice extraction and concentration, followed by fermentation of the extracted juice under submerged (liquid) fermentation conditions. Solid-state fermentation (SStF), occurring in the absence of free water, is a promising alternative approach, potentially offering higher product concentrations, reduced water requirements and liquid effluent from the process, and elimination of the substantial energy requirements of the juice extraction step. While SStF has been applied to various substrates, such as sweet sorghum, there is a lack of studies considering the SStF of sugarcane, which is considered a more challenging substrate. The present study investigated the SStF of whole, milled sugarcane in 3-L horizontal, rotating reactors, to assess the effect of inoculum size, mixing speed, and particle size on ethanol production. The maximum ethanol concentration and yield were 86.7 g/L and 6.15 g/100 g wet mass (90.5% of the theoretical maximum), respectively, achieved at an inoculum size of 5% (w/w), rotation speed of 5 rpm, and particle size range of 8 to 20 mm. The fermentation was scaled up to a 50 L solid-state reactor, applying intermittent mixing to obtain a similar ethanol concentration and yield of 87.5 g/L and 6.61 g/100 g wet mass, respectively.
Every year a huge amount of organic solid waste is generated globally. This quantity is expected to keep increasing, making sustainable, safe and environmentally responsible management of solid waste vitally important. Composting offers a circular and low-impact route to managing and treating organic solid waste and produces a nutrient rich medium with uses in horticulture and agriculture.
Beginning with a solid introduction to the fundamentals of composting, including bioreactor engineering, energy and mass transfer issues and microbiology, this book then moves on to more complex topics such as compost stability, gaseous emissions and compost uses. With a focus on sustainability, the role of composting in biorefineries and how composting can complement other technologies such as anaerobic digestion and solid-state fermentation are also discussed.
This book is a great resource for both students and researchers with an interest in organic waste management, sustainability or the circular economy.
Solid-state fermentation (SSF) is a process used to produce enzymes and secondary metabolites; however, its low efficiency limits its application, as it does not cost-effectively meet market demand. This article proposes modeling the operation and determining the optimal parameters of SSF processes through the application of artificial intelligence systems. To this end, programming algorithms were designed in MATLAB software to implement an artificial neural network (ANN), a genetic algorithm (GA), particle swarm optimization (PSO), and the artificial bee colony (ABC) algorithm. To verify the proposed method, the production of proteases used in the cheese industry was modeled and optimized. The results show that the optimal process parameters were correctly identified, the modeling precision and accuracy were increased (R² > 0.90), and the process resources required can be reduced. These findings suggest that the use of artificial intelligence systems in SSF processes is an effective tool to maximize their production.
Beauveria bassiana PfBb is a new strain with high host specificity to the target pest Phauda flammans. We conducted a series of experiments to optimize the biphasic fermentation system of B. bassiana PfBb by screening the medium compositions and fermentation environmental conditions in both liquid and solid fermentations. In the liquid fermentation, glucose and yeast extract with a C:N ratio of 17:1 were the optimal carbon and nitrogen sources, respectively, for B. bassiana PfBb mycelium growth and blastospore production, and liquid fermentation with an inoculation concentration of 1 × 10⁸/mL and an inoculum content of 50 mL conidial suspension, at 180 rpm/min rotation speed, pH 7 and 26 °C, favored mycelium growth. However, additional trace elements did not significantly improve liquid fermentation. In the solid fermentation, wheat bran and chaff at a ratio of 8:2 were identified as the best substrates that facilitated B. bassiana PfBb sporulation and conidial germination, and optimal substrates with 20% inoculum content, 50% water content, and 3-day fermentation in darkness had the highest conidia yield. The resulting conidia, stored at −20, 4, and 20 °C for one year, did not significantly change the water content, and with prolonged storage duration, conidial germination was significantly higher at −20 and 4 °C. Moreover, conidia stored at 4 °C for one year maintained its validity and virulence, which were toxic to all instar larvae of P. flammans. Our results provide essential support for the commercial production of B. bassiana PfBb-based biopesticides.
Pine wilt disease (PWD), caused by the pine wood nematode (PWN, Bursaphelenchus xylophilus), is one of the most serious threats to pine forests worldwide. The fungus Esteya vermicola, with its lunate conidia capable of parasitizing the PWN, has shown promise as an efficient biological control agent against PWD. Solid-state fermentation (SSF) is preferred for large-scale applications in the field, as it facilitates microbial agent transport and ensures a long shelf life. However, research on enhancing the yield of lunate conidia from E. vermicola through SSF is limited. In this study, we initially achieved a yield of 3.04 × 10⁸ conidia/g using a basic SSF medium composed of wheat bran, corn flour, and soybean flour. To improve this yield, we employed an orthogonal experimental design (OED) to identify the optimal medium composition, which required a wheat bran-to-corn flour-to soybean flour ratio of 7:2:1 (w/w/w), a substrate-to-water ratio of 1:0.7 (w/v), and the addition of 1.33% (w/w) glucose, 1.33% (w/w) yeast extract fermentation, and 1.33% (w/w) MgSO4. Using the response surface methodology (RSM), we calculated the optimal fermentation conditions, which were 24.9 °C, 78.0% relative humidity (RH), an inoculation volume of 16.3% (v/w), and a fermentation time of 7.1 days. Under these conditions, the yield of lunate conidia reached a maximum of 16.58 × 10⁸ conidia/g, a 4.45-fold increase after optimization. This study improved the yield of E. vermicola lunate conidia and provides insights for developing biopesticides based on this strain.
Solid-state fermentation (SSF) has gained considerable attention due to its potential in the production of bioactive compounds from agroindustrial residues, aligning with circular economy targets. This review examines the core bases involved in SSF with a focus on bioreactor engineering. The review underlines the microorganisms metabolic activities under different operational conditions and focuses on engineering challenges encountered in designing packed-bed bioreactors, including an analysis of the interaction between microbial growth kinetics and transport phenomena. Finally, given its essential role in the scaling-up process, this review discusses mathematical modeling developed for SSF in packed-bed bioreactors, establishing a foundation for the future development of more efficient, scalable, and sustainable SSF-based applications.
Global protein consumption is increasing exponentially, which requires efficient identification of potential, healthy, and simple protein sources to fulfil the demands. The existing sources of animal proteins are high in fat and low in fiber composition, which might cause serious health risks when consumed regularly. Moreover, protein production from animal sources can negatively affect the environment, as it often requires more energy and natural resources and contributes to greenhouse gas emissions. Thus, finding alternative plant-based protein sources becomes indispensable. Rapeseed is an important oilseed crop and the world’s third leading oil source. Rapeseed byproducts, such as seed cakes or meals, are considered the best alternative protein source after soybean owing to their promising protein profile (30%–60% crude protein) to supplement dietary requirements. After oil extraction, these rapeseed byproducts can be utilized as food for human consumption and animal feed. However, anti-nutritional factors (ANFs) like glucosinolates, phytic acid, tannins, and sinapines make them unsuitable for direct consumption. Techniques like microbial fermentation, advanced breeding, and genome editing can improve protein quality, reduce ANFs in rapeseed byproducts, and facilitate their usage in the food and feed industry. This review summarizes these approaches and offers the best bio-nutrition breakthroughs to develop nutrient-rich rapeseed byproducts as plant-based protein sources.
An adhesive solid-state fermentation (adSSF) mode was developed to produce Aspergillus niger conidia, which used a stainless-steel Dixon ring as the support and water-retaining adhesive to load nutritional media on its surface. To obtain high conidia yields, the components of the water-retaining adhesive were screened, optimized by single-factor optimization and response surface methodology, and the optimal dosages of the main components were: wheat bran powder 0.023 g·cm⁻³bed, cassava starch 0.0022 g·cm⁻³bed, and xanthan gum 0.0083 g·cm⁻³bed. The experimentally tested conidia yield was 4.2-fold that without water-retaining adhesive but was 3.7% lower than the maximum yield predicted by the model. The observed double-side growth of A. niger on the Dixon ring supports improved space utilization of the fermentation bed, and the void fraction can increase with the shrinkage of the gel layer. In 1.6 L tray reactors with three-point online temperature monitoring, the inner-bed temperature of adSSF was at most 4 °C lower than the adsorbed carrier solid-state fermentation (ACSSF) mode, and the conidia yield was 1.68 × 10⁸conidia.cm⁻³bed, 61.5% higher than that of the ACSSF bed at the same time, but when the fermentation time was extended to 168 h, the conidia yield of the adSSF bed and ACSSF bed were close to each other. The results revealed that the high voidage of the adSSF bed was the main reason for low bed temperature, which can benefit the inner-bed natural convection and water evaporation.
Graphical Abstract
Solid-state fermentation (SSF) is the bioprocess where microorganisms are cultivated in the absence of free water under controlled conditions. Lactic acid can be produced by Rhizopus oryzae SSF of grape stalks. During the microorganism’s growth, the temperature and water content of the solid bed fluctuate, leading to areas of either dry or excessive moisture in the solid substrate. Therefore, it is crucial to control the water supply to the matrix. In this work, we obtain lactic acid through SSF of grape stalks using Rhizopus oryzae NCIM 1299. The SSF was conducted at a fixed temperature of 35 °C, with five constant relative humidity (RH) levels: 50, 57, 65, 72, and 80%RH. Mathematical models, including the Logistic and First-Order Plus Dead-Time models for fungal biomass growth and the Luedeking and Piret with Delay Time model for lactic acid production, were adjusted to kinetic curves. Growth kinetic parameters (Xmax, μmax, Tp, T0, Yp/x, and td) were determined for all conditions. These kinetic parameters were then correlated with relative humidity using a second-degree polynomial relationship. We observed a decrease in Xmax with an increasing %RH, while the value of Yp/x increased at a higher %RH. Finally, the optimal variable relative humidity profile was obtained by applying the dynamic optimization technique, resulting in a 16.63% increase in lactic acid production.
Solid-state fermentation (SSF) of cereals with edible fungi is a promising strategy for producing functional flours. Hypothetically, the nutritional and functional properties of these flours could be modulated by manipulating substrate composition, fungal species, and incubation conditions. This article reports the variation over time in nutritional, polyphenol, and triterpene contents, as well as the antioxidant activity of rice and wheat fermented with Ganoderma sessile and Pleurotus ostreatus. Solid-state fermentation significantly improved the antioxidant power of the substrates which seemed to be highly correlated with the increase of the phenolic compounds. This increase peaked in the 2nd-3rd week and decreased after this point. Triterpene content also increased, especially in substrates fermented with G. sessile. Substrates fermented with G. sessile showed higher values than those fermented with P. ostreatus in all compounds, which could be a result of a higher growth rate. Fermented wheat showed higher values than fermented rice in all measured compounds except reducing sugars which can be related to a slower progress in the fermentation due to the more complex structure of the wheat grain. Our results reinforce the importance of substrate and strain selection for product modulation to meet the industry's growing needs.
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