Marica Rakin

PROGRESS IN THE PRODUCTION OF BIOETHANOL ON STARCH-BASED FEEDSTOCKS*

Bioethanol produced from renewable biomass, such as sugar, starch, or lignocellulosic materials, is one of the alternative energy resources, which is both renewable and environmentally friendly. Although, the priority in global future ethanol production is put on lignocellulosic processing, which is considered as one of the most promising second-generation biofuel technologies, the utilization of lignocellulosic material for fuel ethanol is still under improvement. Sugar-based (molasses, sugar cane, sugar beet) and starch-based (corn, wheat, triticale, potato, rice, etc.) feedstock are still currently predominant at the industrial level and they are, so far, economically favorable compared to lingocelluloses. Currently, approx. 80 % of total world ethanol production is obtained from the fermentation of simple sugars by yeast. In Serbia, one of the most suitable and available agricultural raw material for the industrial ethanol production are cereals such as corn, wheat and triticale. In addition, surpluses of this feedstock are being produced in our country constantly. In this paper, a brief review of the state of the art in bioethanol production and biomass availability is given, pointing out the progress possibilities on starch-based production. The progress possibilities are discussed in the domain of feedstock choice and pretreatment, optimization of fermentation, process integration and utilization of the process byproducts.

The bioethanol production with the thin stillage recirculation.

In this paper, the bioethanol production with the thin stillage recirculation in mashing was investigated. The mashing was performed with recirculation of: 0, 10, 20 and 30 % of the thin stillage. The thin stillage recirculation was repeated six times. In the experiment without the thin stillage, the recirculation bioethanol yield (compared to the theoretical yield) was 97.96 %, which implicates that the experiment conditions were chosen and performed well. With the addition of the thin stillage, the bioethanol yield increased and was above 100 %. Higher bioethanol yield than 100 % can be explained by the fact that the thin stillage contains carbohydrates, amino acids and yeast cells degradation products. The bioethanol yield increased with the increased number of thin stillage recirculation cycles. Dry matter content in fermenting slurry increased with the increased thin stillage quantity and the number of the thin stillage recirculation cycles (8.04 % for the first and 9.40 % for the sixth cycle). Dry matter content in thin stillage increased with the increased thin stillage quantity and the number of thin stillage recirculation cycles. Based on the obtained results it can be concluded that thin stillage recirculation increased the bioethanol yield. The highest bioethanol yields were obtained with recirculation of 10% thin stillage.

Effect of different fermentation parameters on L-lactic acid production from liquid distillery stillage

Expansion of lactic acid applications, predominantly for the preparation of biodegradable polymers increased the research interest for new, economically favourable production processes. Liquid stillage from bioethanol production can be an inexpensive, valuable source of nutrients for growth of lactic acid bacteria. Utilisation of residual biomass with spent fermentation media as a functional animal feed can greatly influence the process value and its ecological aspect. In this paper, the kinetics of lactic acid and biomass production on liquid stillage by Lactobacillus rhamnosus ATCC 7469 was studied. In addition, the impact of temperature, inoculum concentration, shaking and pH control by addition of CaCO(3) was evaluated. Maximal lactic acid yield of 73.4%, as well as high biomass production (3×10(8) CFU ml(-1)) were achieved under selected conditions (41°C, 5% (v/v) of inoculum, 1% (w/v) of CaCO(3), initial pH of 6.5 and shaking rate of 90 rpm). These results were achieved without supplementation of the stillage with nitrogen or mineral sources.

Functional, rheological and sensory properties of probiotic milk chocolate produced in a ball mill

The aim of this study was to investigate the survival of probiotics (Lactobacillus acidophilus NCFM, Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019) in milk chocolate masses prepared at temperatures 35 °C and 40 °C. The influence of probiotics and preparation temperature on rheology, particle size distribution and sensory properties of the chocolates, was examined during 6 months of storage at 20 ± 2 °C. An inoculation temperature of 40 °C significantly improves the rheological and sensory properties of probiotic chocolate, as well as leading to the survival of L. acidophilus NCFM and L. rhamnosus HN001 strains. After 6 months of storage, the survival of these strains was above 90%, with a viable cell count of about 8.1 log(CFU g−1). An inoculation temperature of 40 °C provides higher scores of overall sensory quality (4.52–4.68), higher quality category (excellent), lower maximal viscosity (for 1.2 Pa s) of chocolates, than a temperature of 35 °C. Compared to the chocolate without probiotics, those inoculated at 40 °C achieved less increase in volume weighted mean diameter distribution (average 0.8%) than chocolates inoculated at 35 °C. Based on the results reported in this paper, seeding of the probiotics in industrial conditions can be done in the mixing tank (at 40 °C) before the phase of chocolate shaping. Addition of probiotics at this stage facilitates the manufacturing process, improves the overall quality of chocolate and preserves the probiotics as a key component of this type of product.

Influence of Chitosan Coating on Mechanical Stability of Biopolymer Carriers with Probiotic Starter Culture in Fermented Whey Beverages

The aim of this study was to improve the mechanical stability of biopolymer carriers and cell viability with addition of chitosan coating during fermentation process and product storage. Dairy starter culture (1% (w/v)) was diluted in whey and mixed with sodium alginate solution and the beads were made using extrusion technique. The mechanical stability of coated and uncoated beads, the release behavior, and the viability of encapsulated probiotic dairy starter culture in fermented whey beverages were analyzed. The mechanical properties of the beads were determined according to force-displacement and engineering stress-strain curves obtained after compression testing. It was observed that addition of chitosan as a coating on the beads as well as the fermentation process increased the elastic modulus of the calcium alginate-whey beads and cell survival. The current study revealed that the coating did not significantly improve the viability of probiotics during the fermentation but had an important influence on preservation of the strength of the carrier during storage. Our results indicate that whey-based substrate has positive effect on the mechanical stability of biopolymer beads with encapsulated probiotics.

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.

The Contribution of Bioactive Peptides of Whey to Quality of Food Products

Abstract Whey proteins are sources of biologically active peptides that can be released by controlled enzymatic hydrolysis or bacterial activity. Whey peptides have a wide range of bioactivities (ACE-inhibitory activity, antioxidant activity, antiinflammatory, antimicrobial), so these peptides are more suitable as ingredients in functional foods than molecules with only one substantial characteristic. Bioactive peptides derived from whey protein and added into probiotic-fermented products and confectionery products (as chocolate, biscuit, or cream) affect human health directly and indirectly. These peptides increase the viable number of probiotic bacteria, increase the stability of the probiotic products, and act in the human organism as antioxidants and ACE inhibitors, increase proliferation of intestinal epithelial cells, and so forth. Bioactive peptides are suitable for application in food because of the simple procedure to produce and separate it. In summary, this chapter describes the biological activity of peptides and their practical application in food products.