Chapter 23 - Solid-State Fermentation Strategy for Microbial Metabolites Production: An Overview

Microflora for improving the Auricularia auricula spent mushroom substrate for Protaetia brevitarsis production

Solid-state fermentation (SSF) technology has been rapidly developed for the past 10 years as a production platform for secondary metabolites, biofuels, food, and pharmaceuticals. Yet, the main drawback of SSF is the local temperature rise of up to 20 K, which potentially reduces the strain activity and inactivates heat sensible products. Due to the low heat capacity and thermal conductivity of mixtures of air with plant material, in comparison to aqueous suspensions in submerged fermentations, heat from metabolic processes is less efficiently dissipated. The exact knowledge of the metabolic heat generation during SSF processes is crucial to guide strategies against overheating. In this work, a simple method using a cost-efficient multichannel instrument is proposed, which allows the determination of heat generation during SSF processes. This method was successfully tested and validated with Blakeslea trispora producing β-carotene during growth on barley. Additionally, the consequences of the generated metabolic heat during SSF on temperature rise and water evaporation were discussed. Finally, changes in growth and product concentration could also be detected by the heat signal, implying the potential as a timesaving screening method.

<p>Solid-state fermentation (SSF) process appears to be an efficient way to recover and valorise organic residues from industries and to generate other products of industrial significance, such as enzymes. As the reproducibility of SSF is one of the main drawbacks in the development of this process, a complete study on this point was carried out. Materials with high nitrogen content, soy waste (SW) and hair waste (HW), were treated by SSF to obtain both proteases for different uses and a stabilized material for soil amendment. The bench scale reactors used in the experiments had a 4.5 l volume. Eight and five experiments were performed with the SW and HW, respectively, over a period of 2.5 years with different batches of each material. The highest production of proteases was observed after 3 days and after 14 days of fermentation, for soy and hair wastes, respectively. In the case of hair waste (HW), the overall CV was close to 4.0% for both the maximum protease activity (PA) and the maximum specific protease activity (sPA). In the case of SW, the overall CVs recorded were 43% and 18.6% for the maximum PA and the maximum sPA, respectively. This demonstrates that SSF can be a reproducible process in bench scale reactors. This is the first study and a help to researchers to develop SSF experiments in a consistent and conclusive way.Solid-state fermentation (SSF) process appears to be an efficient way to recover and valorise organic residues from industries and to generate other products of industrial significance, such as enzymes. As the reproducibility of SSF is one of the main drawbacks in the development of this process, a complete study on this point was carried out. Materials with high nitrogen content, soy waste (SW) and hair waste (HW), were treated by SSF to obtain both proteases for different uses and a stabilized material for soil amendment. The bench scale reactors used in the experiments had a 4.5 l volume. Eight and five experiments were performed with the SW and HW, respectively, over a period of 2.5 years with different batches of each material. The highest production of proteases was observed after 3 days and after 14 days of fermentation, for soy and hair wastes, respectively. In the case of hair waste (HW), the overall CV was close to 4.0% for both the maximum protease activity (PA) and the maximum specific protease activity (sPA). In the case of SW, the overall CVs recorded were 43% and 18.6% for the maximum PA and the maximum sPA, respectively. This demonstrates that SSF can be a reproducible process in bench scale reactors. This is the first study and a help to researchers to develop SSF experiments in a consistent and conclusive way.</p>

Solid-state fermentation (SSF) is the growth of microorganisms without free flowing liquid phase. The history of SSF is very well known to those in the fields of food processing and pharmaceuticals as it is widely applied to the production of several organic acids, flavourings compounds, enzymes and other microbial metabolites of human importance. SSF has been recently considered as the most cheapest and more environmentally friendly relative to submerged liquid fermentation (SLF) in the production of value added industrial based products such as enzymes, bio fuels and the likes. The comparison of SSF and liquid State Fermentation (LSF) has been summarized in a tabular form. The main microorganisms that occupied a pivotal position in achieving absolute SSF processes have been highlighted. A typical bioreactor has been addressed within the concept of SSF. The applications of the process in various economic sectors such as industrial fermentation, agro food industry and environmental control have been reported. Biomass measurement formula is shown, as well as environmental factors, both essential for studying and optimising solid substrate fermentations. SSF is advantageous and appropriate for production of many value added products like enzymes, antibiotics, and organic acids. This technique not only decreases the cost of the process but also makes product cheaper for consumers. This review aimed at gathering the disperse literature on the current state of art on SSF as it concerns biomass and metabolites formation.

Solid-state fermentation (SSF) involves the growth of microorganisms on moist solid substrates in the absence of free water. This low moisture content makes the SSF different from submerged fermentation. Unlike the situation in submerged fermentation there is no systematic study guiding the design and operation of large scale SSF with proper controls. The understanding and modeling of microbial growth kinetics and transport phenomena play important roles in the SSF. The design of bioreactors from tray type to stirred tank is discussed. The packed bed, rotating drum, rocking drum, fluidized bed and stirred tank reactors are used in SSF with and without modifications. The parameters like pH, temperature, agitation and aeration also need to be controlled. There is a large gradient of temperature throughout the trays. By manipulating the nitrogen source requirement, the pH of the system is generally controlled. The different factors that control the agitation and aeration in the SSF are discussed. Finally the advantages and disadvantages of SSF compared to submerged fermentation were mentioned. Moreover, such understanding is very much required in the design, scale up and process control in SSF. This paper deals with the influence of environmental parameters such as airflow rate, temperature, pH, substrate concentration and other physico-chemical parameters on the production of specific metabolites.

The increasing growth of agroindustrial activity resulting in excessive amounts of agriwaste has led to the accumulation of a large quantity of lignocellulosic residues all over the world, in particular in deforestation initiatives for the removal of invasive trees in South Africa. These lignocellulosic residues are rich in energy resources and consist of a mixture of natural polymers based on lignin, cellulose, and hemicellulose. The use of lignolytic fungi such as mushrooms in solid-state fermentation could sufficiently degrade the indigestible lignocellulosic components and add medicinal and nutritional value to otherwise unusable, high-energy waste material, which in turn could yield a new method of producing energy-rich fodder for ruminant animals. The digestive type of animal for which the potential feed is developed must be identified and considered before deciding on the bioconversion method and process, as the outcomes for obtaining potentially high-quality feeds for nonruminant and ruminant animals are different. The current study presents data on the bioconversion of lignocellulosic substrate using solid-state fermentation with edible and medicinal mushrooms, Ganoderma lucidumand Pleurotus ostreatus, and a possible new species, to increase digestibility and nutritional value to be applied as ruminant animal feed. The solid-state fermentation process was optimized and the resulting product was analyzed for the degradation of the lignocellulosic components. Results indicated that the solid-state fermentation duration and mushroom species were key components in achieving significant degradation. Data obtained after 18 weeks of degradation indicated a significant (p < 0.05) reduction in the acid detergent fiber, acid detergent lignin, and neutral detergent fiber fractions of the biomass, with up to a 20% reduction in indigestible components. This increase in digestibility could contribute to increased energy availability for ruminant animals.

Recent process developments in solid-state fermentation

A much cheaper method to separate ethanol after solid-state fermentation process in renewable energy production

Filamentous fungi, especially basidiomycetes, produce a wide range of metabolites, many of which have potential biotechnological and industrial applications. Solid-state fermentation (SSF) is very suitable for the cultivation of basidiomycetes since it mimics the natural habitat of these fungi. Some of the major advantages of SSF are the robustness of the process, the use of low-cost residual materials as substrates, and the reduced usage of water. However, monitoring key variables is difficult, which makes process control a challenge. Specifically, it is very difficult to determine the biomass during SSF process involving basidiomycetes. This is problematic, as the biomass is normally a key variable in mass and energy balance equations. Further, the success of fungal SSF processes is often evaluated, in part, based on the growth of the fungus. Direct determination of the dry weight of biomass is impossible and indirect quantification techniques must be used. Over the years, various determination techniques have been developed for the quantification of fungal biomass in SSF processes. The current review gives an overview of various direct and indirect biomass determination methods, discussing their advantages and disadvantages.

Antioxidant phenolics and their microbial production by submerged and solid state fermentation process: A review

It is well known that the solid-state fermentation (SSF) is a new technology with which antibiotics, enzymes, fine chemicals can be obtained by new bioprocesses with improved efficiency (Giovannozzi-Sermanni & Porri 1989; Pandey et al., 2000) if compared to the classical submerged fermentations. SSF processes can be defined as “the growth of microorganisms, mainly fungi, on moist solid materials in the absence of free-flowing water”(Cannel & Moo-Young 1980). In the last few decades SSF has grown quickly in interest and importance and has been used for the production of antibiotics, alkaloids, aroma compounds, plant growth factors, enzymes, biofuel, and also for the bioremediation of polluting compounds.

Dry/Solid-State Fermentative Ethanol Production

Modeling conversion and transport phenomena in solid-state fermentation: A review and perspectives

Comparative analysis of PHAs production by Bacillus megaterium OUAT 016 under submerged and solid-state fermentation.

Lipases have various industrial applications and their production by filamentous fungi in solid state fermentation (SSF) process is of interest. In this work the lipase enzyme production by the mutant Aspergillus niger 11T51A14, which is a well-known lipase producer was studied using wheat bran as substrate. Microorganism used in fermentation process was inoculated at a concentration of 107 spores/gm into the medium containing nitrogen (ammonium sulfate), sunflower soapstock and wheat bran. The SSF process for enzyme production was carried out in aerated columns immersed in a water bath at 32oC for 72 h. The process was studied using a central composite rotatable design 22, where variables tested were the nitrogen concentration (0.32-0.88 % w/w) and the volume of liquid (60.9-89.1 mL). The lipase activity was analyzed in enzymatic extracts. The wheat bran, in the fermentation medium, acted as a carbohydrate source and as an inducer for the lipase production. The maximum enzyme activity found was 153.4 U/gdm, with a nitrogen concentration of 0.6 % and 89.1 mL of volume of liquid. The response surface model demonstrated that higher volume of liquid had a positive effect in lipase activity, while nitrogen concentration showed an optimal range (0.4-0.6%).