The leather industry uses a chemical dehairing process that produces alkaline wastewater and hair as solid waste. A cleaner process is proposed in this work to reduce these environmental impacts. It consists on the valorization of hair waste together with sludge from wastewater treatment by a solid-state fermentation process to obtain proteases that can be used in an enzymatic dehairing process. SSF was undertaken in 4.5 L scale reactors. Neither sterilization of the materials nor inoculation of pure microorganisms was necessary for the development of the process, whereas aeration was provided during the assay to ensure the prevalence of aerobic conditions. Alkaline proteases were produced as a consequence of the degradation of hair. The highest activity of the alkaline protease in crude extracts was determined at 14 days of the process (56270 ± 2632 activity units/g dry sample), after the thermophilic stage. The final organic matter showed a stability degree similar to that of compost in terms of respiration activity. Potential application of the extracted proteases in dehairing cow hides was successfully proved as an alternative to the chemical dehairing process. The results in the efficiency of the dehairing process were similar to those obtained with the chemical process, thus avoiding the need of chemical reagents and strong chemical conditions. The entire process permits the substitution of the chemical process of dehairing by an environmentally friendly enzymatic process, closing the organic matter cycle.

Solid state fermentation (SSF), a process that occurs in the absence or near absence of water, has been used for the production of various high value added products such as enzymes and other organic components. This paper reviews the recent studies reported on the use of SSF for the production of enzymes; lipases, proteases, cellulases, hemicellulases, ligninases, glucoamylases, pectinases and inulinases. The microorganisms used for fermentation are mostly fungi and substrates are waste materials from the agriculture and food industry. This shows the advantages of SSF from an economical and environmental viewpoint. The paper provides an Downloaded by [New York University] at 03:19 04 February 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 update on several issues, viz. wastes, microorganisms and scale-up and control of the process of fermentation in solid-state.

The production of alkaline proteases by solid-state fermentation (SSF) was evaluated. The effect of three agro-industrial residues was examined: coffee husk, hair waste from the tanning industry and soy fibre residues. Soy fibre presented the highest yield for protease production at the laboratory scale (37ºC, 100 g samples). Consequently, experiments with soy fibre (F) and soy fibre with 10 % compost as an inoculum (FC) were performed for 14 days in 4.5 L bench-scale aerobic near-adiabatic reactors. The highest activity occurred under thermophilic conditions and a high respiration activity of 47331 ±1391 U/g dry matter for F and 18750 ± 1596 U/g dry matter for FC, which are much higher values than those reported in other studies. Alkaline proteases showed maximum stability at pH 11 and temperatures of 43.8 ºC (F) and 30ºC (FC), which was determined by a full factorial experimental design. Storage assays demonstrated that 90 % of enzyme activity was preserved for three months by lyophilising or freezing the samples at-80ºC.

This paper presents a study on the combination of mineral carbonation with biomass production. Laboratory experiments were performed to investigate the growth of freshwater green microalgae Scenedesmus obliquus in the presence of dissolving mineral carbonates, such as nahcolite (NaHCO3) and nesquehonite (MgCO3·3H2O) at atmospheric conditions and 25 °C. The cell density of the algae biomass was determined using fluorescence measurements. A biochemical model was implemented to describe the evolution of the biomass and the consumption of carbon substrate. The parameter estimates show that the algae growth kinetics in the presence of either NaHCO3 or MgCO3·3H2O is similar and is comparable to the literature. Moreover, when MgCO3·3H2O is supplied, the algae appear to form clusters, which favor their separation from the solution. Overall, this work analyzes the potential to combine two carbon dioxide (CO2) utilization options, i.e., mineral carbonation and microalgae cultivation, and it demonstrates the feasibility of the process. However, control of the pH and the carbon dosage is required to attain optimal biomass productivity.

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