Model-based Control of Enzyme Yield in Solid-state Fermentation

Evaluation of fermented soybean meal by Bacillus subtilis as an alternative to fishmeal on the growth, and physiological status of Nile tilapia Oreochromis niloticus fingerlings

A feeding trial was conducted to investigate the effect of fermented soybean meal with Bacillus subtilis bacteria on growth performance, feed utilization, carcass composition, and hematological, and histological section of the liver and intestine of Nile tilapia Oreochromis niloticus fingerlings. Commercial soybean meal (SBM) containing 44% Crude Protein (CP) was fermented using the solid-state fermentation method which depended on autoclaving of SBM, then bacterial treatment injection by Bacillus subtilis, and finally incubation at 40C for 72 h then autoclaved to stop the growth of bacteria. Five isonitrogenous (25% crude protein) and isocaloric (4.4 kcal\g gross energy) experimental fish meal-free diets were formulated to compare with a common control diet containing fishmeal and unfermented soybean meal. Diets without fish meal contain fermented soybean meal (FSM) as a sole protein, FSM with corn gluten (CG), FSM with free amino acid methionine (Meth), FSM with corn gluten and methionine, and unfermented soybean meal. Eighteen glass aquaria, 80-L net volume, were used to stock 10 fingerlings (10.0 ± 0.1 g/fish) in each aquarium in the replicates group. The feed amount was given three times daily, six days a week throughout the 98 days experimental period. Fish were weighed biweekly and feed amounts were adjusted based on the new fish weight. Bacterial fermentation enhanced the protein content of commercial soybean meals by 6%. The crude protein of fermented soybean meal increased from 43.44% to 50.67%. Used of FSM as a sole dietary protein source resulted in a decrease in growth rate and feed utilization. However, the incorporation of FSM with corn gluten, and/or methionine amino acid led to an improvement in the performance of fish. Finally, the best final body weight, weight gain, specific growth rate, protein efficiency ratio, and protein productive value were recorded by a fish-fed mixed plant protein diet (FSM + CG + Meth). Also, Hematocrit and red blood cells were not significantly affected including the FSM.

A Critical Evaluation of Recent Studies on Packed-Bed Bioreactors for Solid-State Fermentation

Packed-bed bioreactors are often used for aerobic solid-state fermentation, since the forced aeration supplies O2 and removes metabolic heat from the bed. Motivated by the potential for applications in biorefineries, we review studies conducted on packed-bed bioreactors over the last decade, evaluating the insights these studies provide into how large-scale packed beds should be designed and operated. Many studies have used low superficial air velocities and suffer from preferential airflow, such that parts of the bed are not properly aerated. Moreover, some studies have proposed ineffective strategies, such as reversing the direction of the airflow or introducing air through perforated pipes within the bed. Additionally, many studies have used narrow water-jacketed packed-bed bioreactors, but these bioreactors do not reflect heat removal in wide large-scale packed beds, in which heat removal through the side walls makes a minor contribution. Finally, we conclude that, although some attention has been given to characterizing the porosities, water sorption isotherms and volumetric heat and mass transfer coefficients of substrate beds, this work needs to be extended to cover a wider range of solid substrates, and work needs to be done to characterize how these bed properties change due to microbial growth.

Application of a constrained mixture design for lipase production by Penicillium roqueforti ATCC 10110 under solid-state fermentation and using agro-industrial wastes as substrate

Solid state fermentation (SSF) simulates the natural conditions fungal growth, where the amount of water in the reaction medium must be restricted, thus limiting the use of liquid substrate. An analytical strategy to deal with this limitation is the design of blending with constraints. Thus, the objective of the work was to optimize two constrained waste mixtures for the production of lipase by Penicillium roqueforti ATCC 10110 under SSF, using different substrates that combine solid and liquid waste. For this, the best fermentation time was determined through a fermentative profile, afterwards a restricted-mix design with lower and upper limits of the components of mixture I (cocoa residue, solid palm oil residue and liquid palm oil residue) and II (cocoa residue, mango residue and palm oil residue liquid palm) was applied. By means of Pareto and contour graphs, the maximum production points of lipase in mixtures I (6.67 ± 0.34 U g^-1) and II (6.87 ± 0.35 U g^-1) were obtained. The restricted mixture design proved to be a promising tool in the production of lipase by P. roqueforti ATCC 10110 under SSF since the use of restrictions is useful when intending to combine solid and liquid residues in fermentation processes.

Digital Twins for Bioprocess Control Strategy Development and Realisation

New innovative Digital Twins can represent complex bioprocesses, including the biological, physico-chemical, and chemical reaction kinetics, as well as the mechanical and physical characteristics of the reactors and the involved peripherals. Digital Twins are an ideal tool for the rapid and cost-effective development, realisation and optimisation of control and automation strategies. They may be utilised for the development and implementation of conventional controllers (e.g. temperature, dissolved oxygen, etc.), as well as for advanced control strategies (e.g. control of substrate or metabolite concentrations, multivariable controls), and the development of complete bioprocess control. This chapter describes the requirements Digital Twins must fulfil to be used for bioprocess control strategy development, and implementation and gives an overview of research projects where Digital Twins or "early-stage" Digital Twins were used in this context. Furthermore, applications of Digital Twins for the academic education of future control and bioprocess engineers as well as for the training of future bioreactor operators will be described. Finally, a case study is presented, in which an "early-stage" Digital Twin was applied for the development of control strategies of the fed-batch cultivation of Saccharomyces cerevisiae. Development, realisation and optimisation of control strategies utilising Digital Twins.

Elevated temperatures do not trigger a conserved metabolic network response among thermotolerant yeasts

BACKGROUND

Thermotolerance is a highly desirable trait of microbial cell factories and has been the focus of extensive research. Yeast usually tolerate only a narrow temperature range and just two species, Kluyveromyces marxianus and Ogataea polymorpha have been described to grow at reasonable rates above 40 °C. However, the complex mechanisms of thermotolerance in yeast impede its full comprehension and the rare physiological data at elevated temperatures has so far not been matched with corresponding metabolic analyses.

RESULTS

To elaborate on the metabolic network response to increased fermentation temperatures of up to 49 °C, comprehensive physiological datasets of several Kluyveromyces and Ogataea strains were generated and used for 13C-metabolic flux analyses. While the maximum growth temperature was very similar in all investigated strains, the metabolic network response to elevated temperatures was not conserved among the different species. In fact, metabolic flux distributions were remarkably irresponsive to increasing temperatures in O. polymorpha, while the K. marxianus strains exhibited extensive flux rerouting at elevated temperatures.

CONCLUSIONS

While a clear mechanism of thermotolerance is not deducible from the fluxome level alone, the generated data can be valued as a knowledge repository for using temperature to modulate the metabolic activity towards engineering goals.

Solid bioprocess of tarbush (Flourensia cernua) leaves for β-glucosidase production by Aspergillus niger: initial approach to fiber-glycoside interaction for enzyme induction

Commercial cellulase production has increased in recent years and consistent research has been carried out to improve levels of β-glucosidase. Bioprocesses have been successfully adapted to produce this enzyme, with solid-state fermentations as the best-suited technique involving fungi. The aim of this study was to use leaves of tarbush (Flourensia cernua), an abundant shrub of the Chihuahuan Desert, as a carbon source for β-glucosidase production by Aspergillus niger. During the solid bioprocess, this enzyme reached its peak production at 36 h of culture with 3876.6 U/L. There is a particular interest in the substrate composition because of the possibility of phenolic glycosides having an important role in β-glucosidase production. HPLC-MS analyses showed that glycosides were present with the highest accumulation at 36 h of fungal culture. Luteolin and apigenin glycosides [1.8 and 2.4 absorbance units, respectively] were also detected and showed their highest point of detection alongside the highest β-glucosidase activity. No apparent changes in cellulose were observed, while hemicellulose content decreased, which could be related to production and activity of β-glucosidase. This study shows that leaves of F. cernua are an important raw material for β-glucosidase production and give a source of compounds of added value which also may have an important role for β-glucosidase production.