Estimation of growth in solid state fermentation: A review

@#Carleysmith and Fox (1984) stated “without doubt, the single most vital yet most problematical value sought duringfermentation is biomass estimation”. Achieving a positive result in determining biomass remains a major challenge insolid state fermentation (SSF). Fungi are well-characterised microorganisms and are widely used in SSF due to theirability to colonise and penetrate into the solid substrate. The compressed structure of the mycelia and the solid substratedoes not allow a complete recovery of the biomass, which may not be insurmountable. Since the use of a directtechnique such as the dry weight method is impractical, the use of an indirect estimation technique is the only alternative.This review examines strategies that have been used to estimate biomass in SSF. Many promising indirect estimationtechniques are available, which can be classified into six categories as follows; (i) measuring cell components notpresent in the substrate; (ii) measuring biomass component present in both substrate and biomass; (iii) measuring othersecondary metabolites; (iv) measuring metabolic activity; (v) measuring images from direct microscopic observation and(vi) measuring biomass from the substrate matrix. New potential technique and future directions are also discussed inthis review. Although significant advances have been made with the availability of various techniques; however, progresshas been very unsatisfactory. The evaluation of microbial growth in SSF may sometimes become laborious, impracticaland inaccurate. Essentially, this remains another critical issue for monitoring growth. The information of the profile offungal biomass growth throughout any SSF process constitutes an essential parameter in estimation of kinetic variablesand subsequently, scale-up of the process.

The role of Aspergillus oryzae KKB4 in reducing and detoxifying aflatoxin B1 applied in moist-heated corn

Aims: The growth and metabolic activity of Aspergillus oryzae KKB4 in AFB1-contaminated corn and later coincided with AFB1 reduction and detoxification were investigated. Methodology and results: The decreasing of AFB1 amount by A. oryzae KKB4 could be clearly observed if the initial AFB1 concentration in corn was increased. Thus, moist-heated corn was artificially inoculated with Aspergillus flavus FNCC 62C7 to increase AFB1 content. AFB1-contaminated corn was applied as solid substrate and then inoculated with A. oryzae KKB4. During fermentation periods, the growth, metabolic activity, and AFB1 decline were investigated by glucosamine content, water content loss, and AFB1 concentration, respectively. The maximum growth was occurred in 4 thday at 1.499 ± 0.028 g glucosamine/ 100 g dry matter. The metabolic activity was going on up to the end of fermentation days, as shown as water content loss at 0.175 ± 0.007 g/g dry matter. In accordance with the growth and metabolic activity, the amount of AFB1 reduction was 37.04 ng AFB1/g dry matter during 5 days fermentation. According to toxicity analysis, it was found that the residues of AFB1 were not toxic to Bacillus megaterium cells. Conclusion, significance and impact of study: A. oryzae KKB4 is able to be applied in solid substrates as AFB1 reduction and detoxification agent. These lucrative effects are also important in relation with food and feed safety.

α-Amylase Production on Low-Cost Substrates by Naxibacter sp. Isolated from Mauritian Soils.

Alpha amylase is an important enzyme used in different industries, which degrades starch into smaller disaccharides. Extracellular α-amylase producing organisms were isolated from soil samples from Mauritius and identified by standard biochemical tests. In this study, the high yielding strain was used for amylase production. The potential of four readily available substrates, namely sugarcane bagasse, potato peel, kitchen wastes and banana peel to induce amylase production was investigated. Different parameters like temperature (30ºC, 40ºC, 50ºC, 60ºC & 70ºC), different pH (5.0, 6.0, 7.0, 8.0 & 9.0) and inoculum sizes (10%, 20%, 50%, 100% & 150% v/w) were used for the α-amylase production. It was found that α-amylase production and activity was highest for potato peel at 50ºC at pH 6.0 and inoculum size 50% (v/w). Amylase assays performed at different incubation temperatures (30ºC - 60ºC) and pH (5-9) showed that the amylase worked best at 50ºC and pH 7.Based on results of biochemical tests and 16S ribosomal RNA gene sequences, the isolate was identified to belong to the Betaproteobacteria, closely related to Naxibacter haematophilus (99% sequence similarity to the type strain).

Characterization of Solid State Fermentation Culture Conditions for Growth and Mananase Production by Aspergillus niger USM F4 on Rice Husk in Tray System.

Aim: The study evaluated various fermentation conditions for the production of mannanase. Place and Duration of Study: Industrial Biotechnology Research Laboratory (IBRL), School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang, Malaysia between May 2009 and September 2010. Methodology: Solid substrate fermentation was carried out in a shallow aluminum tray system (16 cm x 16 cm x 5 cm) for maximum mannanase production by Aspergillus niger USM F4 using rice husk as a substrate. Results: The maximum mannanase activity of 119.91 U/g substrate was achieved on the 6 days of cultivation when the optimized physical parameters were used (substrate thickness of 1.6 cm or equivalent to 80 g of 0.75 mm rice husk, moisture content to substrate ratio of 1:1 (w/v), cultivation temperature at room temperature (28±2ºC), inoculum size of 6x106 spores/ml and in static condition (no mixing during the fermentation process). The results showed an increment of about 30.79% of mannanase activity after the optimization (119.91 U/g substrate) compared to before optimization (91.68 U/g substrate). Conclusion: The results obtained from this study revealed that rice husk can be used as a substrate for mannanase production in solid state fermentation process.

Improved calibration of a solid substrate fermentation model

Background: Calibration of dynamic models in biotechnology is challenging. Kinetic models are usually complex and differential equations are highly coupled involving a large number of parameters. In addition, available measurements are scarce and infrequent, and some key variables are often non-measurable. Therefore, effective optimization and statistical analysis methods are crucial to achieve meaningful results. In this research, we apply a metaheuristic scatter search algorithm to calibrate a solid substrate cultivation model. Results: Even though scatter search has shown to be effective for calibrating difficult nonlinear models, we show here that a posteriori analysis can significantly improve the accuracy and reliability of the estimation. Conclusions: Sensibility and correlation analysis helped us detect reliability problems and provided suggestions to improve the design of future experiments.

Producción de enzima fitasa de aspergillus ficuum con residuos agroindustriales en fermentación sumergida y sobre sustrato sólido / Phytase production by aspergillus ficuum in submergida y sobre sustrato solido

Se describe la producción de fitasa mediante cultivos del tipo sumergido (SmF) y sobre sustrato sólido (SSF) con Aspergillus ficuum DSM 932 en medios de cultivos basados en residuos de la agroindustria. La actividad enzimática fitásica se usó como medida indirecta de la producción de la enzima. En SmF, pH 5,3 y 25 ºC, se trabajó en fermentadores de diferentes volúmenes y con el mayor se operó con diferentes niveles de aireación y agitación. En SSF a 25 ºC se usaron placas de Petri. En SmF con un medio basado en cereales se presentó la mejor actividad neta (0,25 FTU/mL) al sexto día para 300 rpm y 0,5 vvm. En SSF, la torta de canola resultó ser el mejor sustrato con una actividad fitásica neta máxima al tercer día de 6,79 FTU/mL de extracto, equivalente a 33,96 FTU/g de sustrato sólido o 56,43 FTU/g de sustrato seco. Aplicando tecnologías de membrana se concentró un extracto de fitasa a partir de una SmF en medio basado en cereales y también fue posible purificar 6,33 veces un extracto de fitasa producido en SSF con torta de canola, diafiltrando tres veces consecutivas el retenido de 100 kDa. La enzima fitasa de la cepa A. ficuum DSM 932 mostró tener un tamaño ≥ 100 kDa.

Phytase production by submerged fermentation (SmF) and solid state fermentation (SSF) using Aspergillus ficuum DSM 932 in agro-waste-based culture media is described here. Phytase enzyme activity was used for the indirect measurement of enzyme production. Fermentation was carried out in SmF, pH 5.3 at 25 ºC with two fermenters having different volumes; the largest one had different levels of aeration and agitation. Petri dishes were used for SSF at 25 °C. A cereal-based medium obtained the best net activity (0.25 FTU mL-1) for SmF on the sixth day at 300 rpm at 0.5 vvm. Canola cake was the best substrate for SSF, having maximum net phytase activity on the third day: 6.79 FTU mL-1 extract, equivalent to 33.96 FTU g-1 solid substrate or 56.43 FTU g-1 dry substrate. A phytase extract was concentrated from an SmF-based medium in cereals by applying membrane technologies. A phytase extract produced in SSF with canola cakes was purified 6.33 times using three consecutive diafiltrations of the 100 kDa retentate. A. ficuum DSM 932 phytase was ≥ 100 kDa in size.