2.1.2. Lactic acid

Lactic acid represents a chemical with a small world market, and the market for traditional applications of lactic acid is estimated to be growing at about 3-5% annually. New products based on lactic acid may increase the world market share significantly, which includes the use of derivatives such as ethyl esters to replace hazardous solvents like chlorinated hydrocarbon solvents in certain industrial applications. In theory, one mole of glucose results in almost two moles of lactic acid. The recovery process for lactic acid is much more sophisticated than that of the ethanol fermentations, involving various precipitations, chromatographic and distillation steps [5].

Lactic acid can be converted to methyl lactate, lactide, and polylactic acid (PLA) by fermentation [89]. The PL A is a biodegradable polymer used as environmentally friendly biodegradable plastic, which can be the replacement for polyethylene terephthalates (PETs) [90]. Recently, attempts have been made to produce PLA homopolymer and its copolymer by direct fermentation by metabolically engineered [91], shows a great potential for utilizing lignocellulosic feedstock for the key biodegradable polymers. Efforts are also under way to develop efficient processes for converting biologically produced lactic and hydroxypropionic acids to methacrylic and acrylic acids [88].

Lactic acid can be produced either chemically or by microbial fermentation. A major disadvantage for chemical synthesis is the racemic mixture of lactic acid. Microbial fermentation offers both utilization of renewable carbohydrates and production of pure L­or D-lactic acid depending on the strain selected. Currently, most of lactic acid production is produced mainly from corn starch. However, the use of lignocellulosic feedstock for lactic acid production appears to be more attractive because they do not impact the food chain for humans. But the process for converting lignocellulosic feedstock into lactic acid is not cost efficient due to the high cost of cellulase enzymes involved in cellulose hydrolysis [92, 93]. In addition, the main bottleneck during the hydrolysis of lignocellulosic feedstock by cellulases is the inhibition on cellulase by glucose and cellobiose, which remarkably slows down the rate of lignocellulosic feedstock hydrolysis [94]. Economic improvements on the process are mainly focused on increasing the lactic acid tolerance, reducing the requirements for complex and cost intensive growth supplements and products recovery [95].

The high content of carboxylic acids in bio-oil is one of the main reasons for its corrosiveness, which damages storage tanks, boilers, and gas turbines. As a consequence, detailed research on the separation of acidic compounds has been carried out under the condition of distillation at 50 °C.

The carboxylic acid content in the refined bio-oil was used to estimate the separation efficiency. Guo et al. (2009b) chose five major acids in bio-oil and studied their separation characteristics. As shown in Fig. 3, the amount of acetic acid, the most abundant acid in bio­oil, was reduced to 1.9 wt% and 0.96 wt% in the MF and HF, respectively. The results indicated that acidic compounds could be effectively separated from the crude bio-oil by means of molecular distillation technology. The LF, which was rich in water and carboxylic acids, was valuable for further catalytic esterification of bio-oil acidic compounds. Both MF and HF could be further upgraded to produce high-quality fuels.

Microbial growth and substrate utilization expressions can be incorporated into mass balances to yield equations that can be used to predict effluent microorganism and substrate concentrations, and thus process efficiency. Continuous flow systems are grouped into two broad categories, suspended-growth and attached-growth processes, depending on whether the process microorganisms are maintained in suspension, or are attached to an inert medium (e. g., rocks, sand, granular activated carbon, or plastic materials). Attached-growth processes are also called fixed-film processes or biofilm processes.

Biosorption has provided an alternative process to the traditional physico-chemical methods, utilizing inexpensive biomass to sequester toxic heavy metals. In the 80 last decades, many researchers have focus on the treatment of wastewater containing heavy metals by the use of living organisms and/or their biomass. Many types of organisms such as bacteria, fungi, yeast and algae or their biomasses, have been used for metal uptake [42].

Biosorption tests batch system are carried out with each strain selected in 500 mL erlenmeyer flask, add 90 mL of a solution containing the metal to study, at an initial concentration established and adding 10 mL culture of 24 h of each strain, with a biomass concentration of 1 g/L. Target used 100 mL of metal solution without bacteria. Samples were
analyzed in duplicate for each strain. Is used nephelometer of McFarland to estimate the number of cells/mL [40, 42]. The conditions established are: pH between 4 and 5, if the metal precipitates at neutral pH, 37 °C and 100 rpm agitation [44, 45]. To read the metal concentration is done by atomic absorption spectrophotometry, taking 5 mL sample every 15 minutes and prepared as described by [23, 46] and the concentration is calculated from the calibration curve prepared with standard solution of each metal studied. The detection limits can be 0.02 mg/L, analyzing in duplicate.

Result from in vitro and in vivo experiments showed that this ingredient has high quality of protein and the amount of digestibility was more than 90% [12] .

In order to determination of artemia meal’s amino acid digestibility, five-week old male broiler chicks were given a semi-purified diet in which artemia meal was the sole source of protein. Apparent amino acid digestibility values of the assay diet, using ileum and excreta contents, were calculated using chromic oxide as indigestible marker. True digestibility values were calculated using endogenous output determined by feeding a nitrogen-free diet. The results showed (Table 2) that in determination of apparent amino acid digestibility of excreta, serine had the lowest (0.80) and methionine had the highest (0.92) digestibility, while glycine had the lowest (0.88) and arginine and leucine had the highest (0.95) apparent ileal digestibility. In measuring true excreta and ileal amino acid digestibility, alanine and glycine had the lowest (0.90 and 0.93) and methionine had the highest (0.96 and 0.99) digestibility, respectively. In general, the site of measurement had no effect on apparent or true amino acid digestibility of artemia meal [2] .

Fed-batch fermentation is described as the type of system where nutrients are added when their concentration falls. In the absence of outlet flow, the volume in the bioreactor will increase linearly. The nutrients are added in several doses to ensure that there are not surplus nutrients in the fermenter at any time. Surplus nutrients may inhibit microorganism growth. By adding nutrients little by little, the reaction can proceed at a high production rate without getting overloaded. The best way to control the addition of the feed is monitoring the concentration of the nutrient itself in the fermenter or reactor vessel.

The main advantages of the fed batch fermenter are:

a. The extension of the exponential growth phase and production of metabolites of interest.

b. The production of high biomass and product concentrations.

c. The reduced inhibition by the substrate.

However, accumulations of toxic products to the microorganism in the medium and downtime due to charging and discharging (which also occur in batch fermentations) are the main disadvantages of Fed batch fermentation [12].

Ecuador is a very rich country in terms of biomass, produced by agricultural activities as well as biomass from natural forests. Nevertheless, this biomass is now misused and underestimated, because of the lack of mature technologies to take the best from it.

Ecuador has a high potential for the production of lignocellulosic ethanol, if we take a look of the amount of lignocellulosic waste materials that are being produced every year in crops such as bananas, palm oil, sugar cane, etc. Nevertheless it is to be understood that social and economic costumes are deeply rooted so it’s going to be a big task changing the current uses of several waste materials. The case of empty fruit bunches is a typical example where it is possible to analyze the behaviors and preferences of the farmers and industry people.

It is necessary to establish rules and laws to regulate the raising biomass markets, moreover if the biomass is going to be transformed in valuable and useful products such as xylitol, ethanol, foods and renewable chemicals.

The technologies are being improved to get better yields and lower production costs. A demonstrative scale biorefinery has recently sat up in Ecuador at the Neotropical Center for the Biomass Research, under the Pontificia Universidad Catolica del Ecuador. This biorefinery was completely designed and constructed in Ecuador and is the very first in its genus in the country as well as one of the few in South America.

Author details

Enrique Javier Carvajal Barriga, Patricia Portero Barahona, Edgar Salas, Carolina Tufino and Bernardo Bastidas

Pontificia Universidad Catolica del Ecuador, Centro Neotropical para la Investigation de la Biomasa, Quito-Ecuador

Cristina Guaman-Burneo

Departamento de Microbiologia, ICB, C. P. 486, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil

Acknowledgement

The authors want to acknowledge the Pontificia Universidad Catolica del Ecuador and the SENESCYT (Secretariat of Science and Technology of Ecuador) for financing the RESETA project and scientific activities at the Neotropical Center for the Biomass Research.

Second generation bioethanol which made from lignocellulosic biomass or woody crops, agricultural residues or waste is considered a future replacement for the food crops that are currently used as feedstock for bioethanol production. Technology for producing bioethanol from biomass is moving out of the laboratory and into the commercial place. Breakthroughs in bioethanol technology in the past decade has lead to commercialization of biomass conversion technology. In U. S alone, Six companies were listed by the U. S Environmental

Protection Agency (EPA) as cellulosic ethanol producers, and their combined anticipated production volume is 8 million ethanol-equivalent gallons for coming years [23]. The six companies are DuPont Danisco Cellulosic Ethanol LLC, Fiberight LLC, Fulcrum Bioenergy Inc., Ineos Bio, KL Energy Corp. and ZeaChem Inc. In April 2011, Mossi & Ghisolfi Group (M&G) (Chemtex) commenced construction of a commercial-scale 13 million gallons/year (50 million liters) cellulosic ethanol production facility in Crescentino, Italy. Beside that, there is Abengoa Company, which has a 5m litre/year demonstration plant at Salamanca, Spain. In October 2010, Norway-based cellulosic ethanol technology developer Weyland commenced production at its 200,000 liter (approximately 53,000 gallon) pilot-scale facility in Bergen, Norway. In Asia, Nippon Oil Corporation and other Japanese manufacturers including Toyota Motor Corporation plan to set up a research body to develop cellulose — derived biofuels. The consortium plans to produce 250,000 kilolitres (1.6 million barrels) per year of bioethanol by March 2014. In China, cellulosic ethanol plant engineered by SunOpta Inc. and owned and operated by China Resources Alcohol Corporation that is currently producing cellulosic ethanol from corn stover (stalks and leaves) on a continuous, 24-hour per day basis.

A way to improve the effect of LHW fractionation is to add an external acid or alkali, which can catalyze the solubilisation of the hemicellulose, reduce the optimal pre-treatment temperature and gives a better enzymatic hydrolysable substrate [162-164].

Acid pre-treatments can be performed with concentrated or diluted acid. However utilization of concentrated acid is less attractive for ethanol production due to the formation of inhibiting compounds, and high acid concentration (e. g. 30-70%) in the concentrated-acid process makes it extremely corrosive and dangerous [165, 166]. Diluted acid pre-treatment appears as more favourable method for industrial applications and have been studied for fractionation wide range of lignocellulosic feedstocks, including softwood, hardwood, herbaceous crops, agricultural residues, wastepaper, and municipal solid waste. It performed well on most biomass materials, mainly xylan, but also converting solubilised hemicellulose to fermentable sugars. Of all acid-based pre-treatment methods, sulphuric acid has been most extensively studied since it is inexpensive and effective. Organic acids such as fumaric or maleic acids are appearing as alternatives to pre-treat LCF for fractionation. Organic acids also can pre-treat lignocellulosic materials with high efficiency although fumaric acid was less effective than maleic acid. Furthermore, less amount of furfural was formed in the maleic and fumaric acid pre-treatments than with sulphuric acid [167]. Phosphoric acid, hydrochloric acid and nitric acid have also been tested [34].

enzyme to the cellulose. Alkali pre-treatment can be used at room temperature and times ranging from seconds to days. It is reported to cause less sugar degradation than acid pre­treatment. It is basically a delignification process, in which a significant amount of hemicellulose is solubilised as well. Alkaline pre-treatment of lignocellulosic materials causes swelling, increasing the internal surface of cellulose and decreasing the degree of polymerization and crystallinity, which provokes lignin structure disruption, and separation of structural linkages between lignin and carbohydrates [117]. In general, alkaline pre­treatment is more effective on hardwood, herbaceous crops, and agricultural residues with low lignin content than on softwood with high lignin content [168]. Alkali pre-treatment was shown to be more effective on agricultural residues than on wood materials [169]. Addition of an oxidant agent (oxygen/H2O2) to alkaline pre-treatment (NaOH/Ca(OH)2) can favour lignin removal to improve the performance [170].

1.2.1. Establishment year

All operations carried out in a willow stand during the first year are aimed at promoting plant establishment and a high survival rate, thereby ensuring the on-going productive life of the plantation. Weeds are the main problem encountered in willow crop, and they may still colonise fields despite pre-emergence treatments. It was established decades ago that during the first year after planting, vigorous weeds reduce willow growth by between 50% and 90% [36]. Most of these invasive species have higher growth rates than young willow shoots, and compete with them mainly for light [37], and to a lesser extent for water and nutriments, leading to high plant mortality within the first few months. Hence, great care should be taken to control weed development in the field in the weeks following planting. On most willow plantations in Quebec, one to three passes with a rotary tiller cultivator between rows are needed to control weeds during the establishment year. In case of a severe weed problem, manual weeding may be required between plants within each row.

Polyacrylamide gels are formed by polymerization of acrylamide by the action of a crosslinked agent, is chemically inert, uniform properties, able to be prepared quickly and reproducibly. Thus, in addition, transparent gels with mechanical stability, water insoluble, relatively non-ionic and allow good visualization of the bands for a long time. Also has the advantage that by varying the concentration of polymers can be modified in a controlled manner the pore size, there sometimes is used in diagnosis least because of their neurotoxocidad [59].

Whole cell immobilization within a polyacrylamide gel also provides a useful laboratory scale system and has been used to biosorb and recover a number of heavy metal(s). Good results have been obtained in the case of polyacrylamide immobilized cells of Citrobacter where a very high removal of uranium, cadmium and lead was observed from solutions supplemented with glycerol -2PO4. Rhizopus arrhizus biomass immobilized on polyacrylamide gel was effective in almost completely removing Cu2+ Co2+ and Cd2+ from synthetic metal solution [26, 55].