Experimental design to enhance the production of l-(+)-lactic acid from steam-exploded wood hydrolysate using Rhizopus oryzae in a mixed-acid fermentation

Fumaric acid production by Rhizopus species from acid hydrolysate of oil palm empty fruit bunches

The hemicellulosic fraction of lignocellulosic biomass is a very important material, due to the significant concentration of pentoses present in its composition and that can be used sustainably in biotechnological processes such as the production of fumaric acid. Research efforts are currently being promoted for the proper disposal and valorization of empty fruit bunches (EFB) from oil palm. In this work, seventeen Rhizopus species were evaluated in a fermentation medium with EFB hydrolyzate, without detoxification, as a carbon source for fumaric acid production. Rhizopus circicans 1475 and Rhizopus 3271 achieved productions of 5.65 g.L-1 and 5.25 g.L-1 of fumaric acid at 30 °C, 120 rpm for 96 h, respectively. The percentage of consumed sugars, mainly pentoses, was 24.88% and 34.02% for R. circicans 1475 and R 3271, respectively. Soy peptone and ammonium sulfate were evaluated as nitrogen sources, where soy peptone stimulated the formation of biomass pellets while ammonium sulfate produced mycelia and clamps.

Biotechnological valorization of agro industrial and household wastes for lactic acid production

Lactic acid (LA) is an organic compound used in several industries, such as food, textile, chemical, and pharmaceutical. The global interest  in  this  product  is  due  to  its  use  for  the  synthesis  of  numerous  chemical  compounds,  including  polylactic  acid,  a  biode-gradable thermoplastic and substitute for petroleum-derived plastics. An in-depth overview of the use of industrial and household wastes as inexpensive substrates in order to reduce the cost of LA production is presented. A review is carried out of the biotech-nological aspects that must be taken into account when using some wastes with high transformation potential to produce LA in a submerged  culture,  as  well  recommendations  for  their  use.  The  advantages  and  disadvantages  of  different  types  of  treatments used for the transformation of waste into suitable substrates are considered. Several methods of fermentation, as well as genetic strategies for increasing the production, are summarized and compared. It is expected that in a few years there will be many ad-vances in these areas that will allow greater large-scale production of LA using agroindustrial or household wastes, with potential positive economic and environmental impact in some regions of the planet.

Fermentative lactic acid production from coffee pulp hydrolysate using Bacillus coagulans at laboratory and pilot scales

In this study, the lignocellulosic residue coffee pulp was used as carbon source in fermentative l(+)-lactic acid production using Bacillus coagulans. After thermo-chemical treatment at 121°C for 30min in presence of 0.18molL(-1) H2SO4 and following an enzymatic digestion using Accellerase 1500 carbon-rich hydrolysates were obtained. Two different coffee pulp materials with comparable biomass composition were used, but sugar concentrations in hydrolysates showed variations. The primary sugars were (gL(-1)) glucose (20-30), xylose (15-25), sucrose (5-11) and arabinose (0.7-10). Fermentations were carried out at laboratory (2L) and pilot (50L) scales in presence of 10gL(-1) yeast extract. At pilot scale carbon utilization and lactic acid yield per gram of sugar consumed were 94.65% and 0.78gg(-1), respectively. The productivity was 4.02gL(-1)h(-1). Downstream processing resulted in a pure formulation containing 937gL(-1)l(+)-lactic acid with an optical purity of 99.7%.

Simultaneous saccharification and high titer lactic acid fermentation of corn stover using a newly isolated lactic acid bacterium Pediococcus acidilactici DQ2

A lactic acid bacterium with high tolerance of temperature and lignocellulose derived inhibitor was isolated and characterized as Pediococcus acidilactici DQ2. The strain used in the simultaneous saccharification and fermentation (SSF) for high titer lactic acid production at the high solids loading of corn stover. Corn stover was pretreated using the dry sulphuric acid pretreatment, followed by a biological detoxification to remove the inhibitors produced in the pretreatment. The bioreactor with a novel helical impeller was used to the SSF operation of the pretreated and biodetoxified corn stover. The results show that a typical SSF operation at 48 °C, pH 5.5, and near 30% (w/w) solids loading in both 5 and 50 L bioreactors was demonstrated. The lactic acid titer, yield, and productivity reached 101.9 g/L, 77.2%, and 1.06 g/L/h, respectively. The result provided a practical process option for cellulosic lactic acid production using virgin agriculture lignocellulose residues.

Lactic acid production from lignocellulose-derived sugars using lactic acid bacteria: overview and limits

Lactic acid is an industrially important product with a large and rapidly expanding market due to its attractive and valuable multi-function properties. The economics of lactic acid production by fermentation is dependent on many factors, of which the cost of the raw materials is very significant. It is very expensive when sugars, e.g., glucose, sucrose, starch, etc., are used as the feedstock for lactic acid production. Therefore, lignocellulosic biomass is a promising feedstock for lactic acid production considering its great availability, sustainability, and low cost compared to refined sugars. Despite these advantages, the commercial use of lignocellulose for lactic acid production is still problematic. This review describes the "conventional" processes for producing lactic acid from lignocellulosic materials with lactic acid bacteria. These processes include: pretreatment of the biomass, enzyme hydrolysis to obtain fermentable sugars, fermentation technologies, and separation and purification of lactic acid. In addition, the difficulties associated with using this biomass for lactic acid production are especially introduced and several key properties that should be targeted for low-cost and advanced fermentation processes are pointed out. We also discuss the metabolism of lignocellulose-derived sugars by lactic acid bacteria.

New trends and challenges in lactic acid production on renewable biomass

Lactic acid is a relatively cheap chemical with a wide range of applications: as a preservative and acidifying agent in food and dairy industry, a monomer for biodegradable poly-lactide polymers (PLA) in pharmaceutical industry, precursor and chemical feedstock for chemical, textile and leather industries. Traditional raw materials for fermentative production of lactic acid, refined sugars, are now being replaced with starch from corn, rice and other crops for industrial production, with a tendency for utilization of agro industrial wastes. Processes based on renewable waste sources have ecological (zero CO2 emission, eco-friendly by-products) and economical (cheap raw materials, reduction of storage costs) advantages. An intensive research interest has been recently devoted to develop and improve the lactic acid production on more complex industrial by-products, like thin stillage from bioethanol production, corncobs, paper waste, straw etc. Complex and variable chemical composition and purity of these raw materials and high nutritional requirements of Lare the main obstacles in these production processes. Media supplementation to improve the fermentation is an important factor, especially from an economic point of view. Today, a particular challenge is to increase the productivity of lactic acid production on complex renewable biomass. Several strategies are currently being explored for this purpose such as process integration, use of Lwith amylolytic activity, employment of mixed cultures of Land/or utilization of genetically engineered microorganisms. Modern techniques of genetic engineering enable construction of microorganisms with desired characteristics and implementation of single step processes without or with minimal pre-treatment. In addition, new bioreactor constructions (such as membrane bioreactors), utilization of immobilized systems are also being explored. Electrodialysis, bipolar membrane separation process, enhanced filtration techniques etc. can provide some progress in purification technologies, although it is still remaining the most expensive phase in the lactic acid production. A new approach of parallel production of lactic bacteria biomass with probiotic activity and lactic acid could provide additional benefit and profit rise in the production process.

Fuels and chemicals from hemicellulose sugars

Industrial processes of lignocellulosic material have made use of only the hexose component of the cellulose fraction. Pentoses and some minor hexoses present in the hemicellulose fraction, which may represent as much as 40% of lignocellulosic biomass, have in most cases been wasted. The lack of good methods for utilization of hemicellulose sugars is a key obstacle hindering the development of lignocellulose-based ethanol and other biofuels. In this chapter, we focus on the utilization of hemicellulose sugars, the structure of hemicellulose and its hydrolysis, and the biochemistry and process technology involved in their conversion to valuable fuels and chemicals.

Biorefineries--multi product processes

The development of biorefineries represents the key for access to an integrated production of food, feed, chemicals, materials, goods, and fuels of the future [1]. Biorefineries combine the necessary technologies of the biogenic raw materials with those of intermediates and final products. The main focus is directed at the precursors carbohydrates, lignin, oils, and proteins and the combination between biotechnological and chemical conversion of substances. Currently the lignocellulosic feedstock biorefinery, green biorefinery, whole corn biorefinery, and the so-called two-platform concept are favored in research, development, and industrial implementation.

Production of lactic acid and fungal biomass by Rhizopus fungi from food processing waste streams

This study proposed a novel waste utilization bioprocess for production of lactic acid and fungal biomass from waste streams by fungal species of Rhizopus arrhizus 36017 and R. oryzae 2062. The lactic acid and fungal biomass were produced in a single-stage simultaneous saccharification and fermentation process using potato, corn, wheat and pineapple waste streams as production media. R. arrhizus 36017 gave a high lactic acid yield up to 0.94-0.97 g/g of starch or sugars associated with 4-5 g/l of fungal biomass produced, while 17-19 g/l fungal biomass with a lactic acid yield of 0.65-0.76 g/g was produced by the R. oryzae 2062 in 36-48 h fermentation. Supplementation of 2 g/l of ammonium sulfate, yeast extract and peptone stimulated an increase in 8-15% lactic acid yield and 10-20% fungal biomass.

Genetic diversity in Rhizopus oryzae strains as revealed by the sequence of lactate dehydrogenase genes

Twenty-seven strains of Rhizopus oryzae accumulating predominantly lactic acid were shown to possess two ldh genes, ldhA and ldhB, encoding NAD-dependent lactate dehydrogenases. Variation in nucleotide sequence was identified for each gene from different strains, and similar phylogenetic trees were obtained based on the nucleotide sequences of both genes. The other 21 strains of R. oryzae accumulating predominantly fumaric and malic acids contained a single ORF of ldhB. Compared to the strains accumulating predominantly lactic acid, a lower degree of sequence divergence was found in ldhB, resulting in a separate cluster in the phylogenetic tree. The high similarity (>90%) spanning the ORF and adjacent regions demonstrates that ldhA and ldhB are derived from the same ancestor gene. The strains accumulating predominantly fumaric and malic acids lack functional ldhA, which plays a role in lactic acid synthesis and may form a lineage separated from the strains accumulating predominantly lactic acid in the genus Rhizopus.

Production of l-lactic acid from corncob

The optimum temperature, initial pH, amount of added enzyme and substrate (corncob) for the hydrolysis of corncob by Acremonium cellulase were 35 degrees C, 4.5, 10 u/g-corncob and 100 g/l, respectively. Under the optimum conditions, more than 55 g/l of reducing sugars were hydrolyzed from 100 g/l of corncob to 34 g/l of glucose and 12 g/l of xylose based on dried corncob. More than 25 g/l of L-lactic acid was produced from this enzymatic hydrolyzate and less than 5 g/l of xylose remained in the 3-l airlift bioreactor. The production of L-lactic acid by simultaneous saccharification and fermentation (SSF) was also carried out in the 3-l airlift bioreactor using Acremonium thermophilus (cellulose-producer) and Rhizopus sp. MK-96-1196 (lactic acid-producer). More than 24 g/l of L-lactic acid was produced from 100 g/l of untreated raw corncob.

Regulation of expression of the Rhizopus oryzae uricase and urease enzymes

The regulation of intracellular urease and uricase activities was examined in Rhizopus oryzae. Urease activity (2.4 U/mg protein) was present in R. oryzae mycelium grown in minimal medium containing NH4CI as sole nitrogen source. This activity increased threefold under nitrogen derepression conditions, but no induction by urea was detected. Control of urease activity in R. oryzae differs from that found in Neurospora crassa but resembles the situation in Aspergillus nidulans. No uricase activity was detected in R. oryzae mycelium grown in minimal medium containing NH4Cl as sole nitrogen source. Uricase activity was increased 10- to 40-fold under derepression conditions and was induced by exogenous uric acid (60- to 78-fold). Control of the R. oryzae uricase differs from that found in N. crassa and A. nidulans. This is the first analysis of the regulation of enzymes from the purine catabolic pathway in any member of the Zygomycetes.

Production of L(+)-lactic acid from glucose and starch by immobilized cells of Rhizopus oryzae in a rotating fibrous bed bioreactor

A rotating fibrous-bed bioreactor (RFB) was developed for fermentation to produce L(+)-lactic acid from glucose and cornstarch by Rhizopus oryzae. Fungal mycelia were immobilized on cotton cloth in the RFB for a prolonged period to study the fermentation kinetics and process stability. The pH and dissolved oxygen concentration (DO) were found to have significant effects on lactic acid productivity and yield, with pH 6 and 90% DO being the optimal conditions. A high lactic acid yield of 90% (w/w) and productivity of 2.5 g/L.h (467 g/h.m(2)) was obtained from glucose in fed-batch fermentation. When cornstarch was used as the substrate, the lactic acid yield was close to 100% (w/w) and the productivity was 1.65 g/L.h (300 g/h.m(2)). The highest concentration of lactic acid achieved in these fed-batch fermentations was 127 g/L. The immobilized-cells fermentation in the RFB gave a virtually cell-free fermentation broth and provided many advantages over conventional fermentation processes, especially those with freely suspended fungal cells. Without immobilization with the cotton cloth, mycelia grew everywhere in the fermentor and caused serious problems in reactor control and operation and consequently the fermentation was poor in lactic acid production. Oxygen transfer in the RFB was also studied and the volumetric oxygen transfer coefficients under various aeration and agitation conditions were determined and then used to estimate the oxygen transfer rate and uptake rate during the fermentation. The results showed that the oxygen uptake rate increased with increasing DO, indicating that oxygen transfer was limited by the diffusion inside the mycelial layer.

Effects of anaerobic/aerobic incubation and storage temperature on preservation and deodorization of kitchen garbage

To develop a garbage recycling system for the purpose of the production of lactic acid (LA) to use as raw material for producing biodegradable plastics, the preservation and deodorization of garbage during storage are very important. Anaerobic incubation (i.e., storage) was prove to be more suitable than aerobic incubation during the garbage storage in terms of concentration of LA and soluble sugar, pH value, viable bacteria counts and offensive odour substances. This difference is due to a fact that the growth of putrefactive bacteria such as coliforms and Clostridium spp. appeared to be inhibited by anaerobic fermentation during the storage, because the fermentation caused a drop of garbage pH and generated inhibitory substances, i.e., bacteriocins. Under anaerobic condition, LA concentration in the stored garbage was found to be higher in the order: 37 > 25 > 50 > 5 degrees C, and the concentration of sugar accumulated during the 50 degrees C-storage was the highest. Among the conditions employed, the optimum condition for the storage of kitchen garbage was anaerobic at 5 degrees C.

Biotechnological potential of coffee pulp and coffee husk for bioprocesses

Advances in industrial biotechnology offer potential opportunities for economic utilization of agro-industrial residues such as coffee pulp and coffee husk. Coffee pulp or husk is a fibrous mucilagenous material (sub-product) obtained during the processing of coffee cherries by wet or dry process, respectively. Coffee pulp/husk contains some amount of caffeine and tannins, which makes it toxic in nature, resulting the disposal problem. However, it is rich in organic nature, which makes it an ideal substrate for microbial processes for the production of value-added products. Several solutions and alternative uses of the coffee pulp and husk have been attempted. These include as fertilizers, livestock feed, compost, etc. However, these applications utilize only a fraction of available quantity and are not technically very efficient. Attempts have been made to detoxify it for improved application as feed, and to produce several products such as enzymes, organic acids, flavour and aroma compounds, and mushrooms, etc. from coffee pulp/husk. Solid state fermentation has been mostly employed for bioconversion processes. Factorial design experiments offer useful information for the process optimization. This paper reviews the developments on processes and products developed for the value-addition of coffee pulp/husk through the biotechnological means.