J.A.V. Costa

Heat transfer simulation of solid state fermentation in a packed-bed bioreactor

A dynamic two-dimensional mathematical model was developed to simulate the heat transfer in solid state fermentation of rice bran inoculated with Aspergillus niger. Two bioreactors of 47 mm diameter and 300 mm height were used. Forced aeration conditions were simulated and saturated air with 60 ml/g h flow at 30°C and a bed porosity equal to 0.3 were determined as being the optimum operating conditions for the used packed-bed bioreactor.

Vertical tubular photobioreactor for semicontinuous culture of Cyanobium sp.

We evaluated the kinetic culture characteristics of the microalgae Cyanobium sp. grown in vertical tubular photobioreactor in semicontinuous mode. Cultivation was carried out in vertical tubular photobioreactor for 2 L, in 57 d, at 30 °C, 3200 Lux, and 12 h light/dark photoperiod. The maximum specific growth rate was found as 0.127 d(-1), when the culture had blend concentration of 1.0 g L(-1), renewal rate of 50%, and sodium bicarbonate concentration of 1.0 g L(-1). The maximum values of productivity (0.071 g L(-1) d(-1)) and number of cycles (10) were observed in blend concentration of 1.0 g L(-1), renewal rate of 30%, and bicarbonate concentration of 1.0 g L(-1). The results showed the potential of semicontinuous cultivation of Cyanobium sp. in closed tubular bioreactor, combining factors such as blend concentration, renewal rate, and sodium bicarbonate concentration.

Packing density and thermal conductivity determination for rice bran solid-state fermentation

The fermentation of rice bran by Aspergillus niger to produce glucoamylase was carried out in a packed-bed bioreactor. The optimum packing density of medium was between 586 and 858 g/l. Also, thermal conductivity (K) was determined and an experimental correlation with packing density (PD) and moisture (M) was obtained as K = 47.5080 0.0115PD 0.1295M − 6.0737ln(PD) − 5.5555ln(M).

Pentoses and light intensity increase the growth and carbohydrate production and alter the protein profile of Chlorella minutissima

High concentrations of carbon, which is considered a necessary element, are required for microalgal growth. Therefore, the identification of alternative carbon sources available in large quantities is increasingly important. This study evaluated the effects of light variation and pentose addition on the carbohydrate content and protein profile of Chlorella minutissima grown in a raceway photobioreactor. The kinetic parameters, carbohydrate content, and protein profile of Chlorella minutissima and its theoretical potential for ethanol production were estimated. The highest cellular concentrations were obtained with a light intensity of 33.75µmol.m-2.s-1. Arabinose addition combined with a light intensity of 33.75µmol.m-2.s-1 increased the carbohydrate content by 53.8% and theoretically produced 39.1mL·100g-1 ethanol. All of the assays showed that a lower light availability altered the protein profile. The luminous intensity affects xylose and arabinose assimilation and augments the carbohydrate content in C. minutissima, making this microalga appropriate for bioethanol production.

Nitrogen balancing and xylose addition enhances growth capacity and protein content in Chlorella minutissima cultures.

This study aimed to examine the metabolic changes in Chlorella minutissima cells grown under nitrogen-deficient conditions and with the addition of xylose. The cell density, maximum photochemical efficiency, and chlorophyll and lipid levels were measured. The expression of two photosynthetic proteins, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and the beta subunit (AtpB) of adenosine triphosphate synthase, were measured. Comparison of cells grown in medium with a 50% reduction in the nitrogen concentration versus the traditional medium solution revealed that the cells grown under nitrogen-deficient conditions exhibited an increased growth rate, higher maximum cell density (12.7×10(6)cellsmL(-1)), optimal PSII efficiency (0.69) and decreased lipid level (25.08%). This study has taken the first steps toward protein detection in Chlorella minutissima, and the results can be used to optimize the culturing of other microalgae.

Ultrafine fibers of zein and anthocyanins as natural pH indicator

BACKGROUNDnpH-sensitive indicator membranes, which are useful for pharmaceutical, food, and packaging applications, can be formed by encapsulating halochromic compounds within various solid supports. Accordingly, electrospinning is a versatile technique for the development of these indicators, by entrapping pH dyes within ultrafine polymer fibers.nnnRESULTSnThe ultrafine zein fibers, containing 5% (w/v) anthocyanins, had an average diameter of 510u2009nm. The pH-sensitive membrane exhibited color changes from pink to green when exposed to acidic and alkaline buffers, respectively. The contact angle was negligible after 10 and 2u2009s for neat and 5% anthocyanin-loaded zein membranes, respectively.nnnCONCLUSIONnThe pH membranes exhibited color changes in a board pH range, which can potentially be used in various active packaging applications.

Chlorella minutissima cultivation with CO2 and pentoses: Effects on kinetic and nutritional parameters

CO2 emissions and the large quantity of lignocellulosic waste generated by industrialized nations constitute problems that may affect human health as well as the global economy. The objective of this work was to evaluate the effects of using CO2 and pentoses on the growth, protein profile, carbohydrate content and potential ethanol production by fermentation of Chlorella minutissima biomass. CO2 and pentose supplementation can induce changes in the microalgal protein profile. A biomass production of 1.84g.L-1 and a CO2 biofixation rate of 274.63mg.L-1.d-1 were obtained with the use of 20% (v.v-1) CO2. For cultures with 20% (v.v-1) CO2 and reduced nitrogen, the carbohydrate content was 52.3% (w.w-1), and theoretically, 33.9mL.100g-1 of ethanol can be produced. These results demonstrate that C. minutissima cultured with the combined use of CO2 and pentoses generates a biomass with high bioenergetic potential.

Chapter 1 – Advances in Solid-State Fermentation

Abstract Solid-state fermentation (SSF) is a three-phase heterogeneous process, comprising solid, liquid, and gaseous phases, which offers potential benefits for the microbial cultivation for bioprocesses and products development. Over the last two decades, SSF has gained significant attention for the development of industrial bioprocesses, particularly due to lower energy requirement associated with higher product yields and less wastewater production with lesser risk of bacterial contamination. In addition, it is ecofriendly, mostly utilizing solid agro-industrial wastes (resides) as the substrate (source of carbon). SSF processes have enormous potential for many new applications using the bioconversion of agro-industrial residues into biofuels and other high value–added products. SSF offers potential benefits on economic and environmental fronts, with sustainability. This chapter discusses the potential of SSF processes and benefits they offer for the production of industrial processes, including challenges and perspectives.

Chapter 16 – Solid-State Fermentation for the Production of Biosurfactants and Their Applications

Abstract Biosurfactants are active compounds that are produced at the microbial cell surface or excreted, and reduce surface and interfacial tension. Microbial surfactants offer several advantages over synthetic ones, such as low toxicity and high biodegradability, and remain active at extreme pH and salinity. Biosurfactants are produced by bacteria, yeasts, and filamentous fungi. The composition and yield of biosurfactants depends on bioreactor characteristics, pH of the medium, nutrient composition, agitation, oxygen availability, and temperature. Solid-state fermentation conditions allow the use of alternative substrates such as industrial or agricultural by-products to reduce costs. Thus, there is industrial interest in developing large-scale production processes for these compounds. The largest market for biosurfactants is the oil industry; however, the applications are distributed among the various industrial sectors, such as agriculture, cosmetics, and food industries. Based on this, the current chapter reports the processes involved in biosurfactant production.

Innovative polyhydroxybutyrate production by Chlorella fusca grown with pentoses

The current study aimed to evaluate if the addition of pentoses along with variations in light intensity and photoperiod can stimulate the production of polyhydroxybutyrate (PHB) and other biomolecules by Chlorella fusca LEB 111. The variables evaluated were the addition of xylose and arabinose as sources of organic carbon, different photoperiods (18u202fh, 12u202fh and 6u202fh light) and variations in light intensities (58, 28 and 9u202fμmolphotonsu202fm-2u202fs-1). The highest PHB accumulation (17.4%u202fwu202fw-1) and protein production (53.2% ww-1) were observed in assays with xylose addition and a photoperiod of 6u202fh of light provided at 28 and 58u202fμmolphotonsu202fm-2u202fs-1, respectively. The highest lipid content (24.7%u202fwu202fw-1) was obtained with 18u202fh of light. The current study contributes to the development of sustainable alternatives for the use of wastes and the production of biomolecules from algae.