The effect of pretreatment on the invertase activity of gel-entrapped yeast biomass

Summary Gel-entrapped, non-viable yeast biomass with specific invertase activity has been produced by two different pretreatment protocols: a short-time thermal treatment and a brief contact with concentrated ethanol solutions. Four yeast strains were most promising:K. fragilis L-293,C. utilis L-282,S. cerevisiae L-170 and L-209. Of these, the ethanol-tolerant L-282 and the ethanol-tolerant and heat-resistant L-170 gave the most active gel-entrapped biocatalysts: around 2 mg of reducing sugars produced per mg dry yeast per min.     

Effect of enzyme producing microorganisms on the biomass of epigeic earthworms (eisenia fetida) in vermicompost

We analyzed the bacterial community structure of the intestines of earthworms and determined the effect of enzyme producing microorganisms on the biomass of earthworms in vermicompost. Fifty-seven bacterial 16S rDNA clones were identified in the intestines of earthworms by using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis. Entomoplasma somnilux and Bacillus licheniformis were the dominant microorganisms; other strains included Aeromonas, Bacillus, Clostridium, Ferrimonas, and uncultured bacteria. Among these strains, Photobacterium ganghwense, Aeromonas hydrophila, and Paenibacillus motobuensis were enzyme-producing microorganisms. In the mixtures that were inoculated with pure cultures of A. hydrophila WA40 and P. motobuensis WN9, the highest survival rate was 100% and the average number of earthworms, young earthworms, and cocoons were 10, 4.00-4.33, and 3.00-3.33, respectively. In addition, P. motobuensis WN9 increased the growth of earthworms and production of casts in the vermicompost. These results show that earthworms and microorganisms have a symbiotic relationship.     

Recent trends in ionic liquid (IL) tolerant enzymes and microorganisms for biomass conversion

Second generation biofuel production depends on lignocellulosic (LC) biomass transformation into simple sugars and their subsequent fermentation into alcohols. However, the main obstacle in this process is the efficient breakdown of the recalcitrant cellulose to sugar monomers. Hence, efficient feedstock pretreatment and hydrolysis are necessary to produce a cost effective biofuel. Recently, ionic liquids (ILs) have been recognized as a promising solvent able to dissolve different biomass feedstocks, providing higher sugar yields. However, most of the hydrolytic enzymes and microorganisms are inactivated, completely or partially, in the presence of even low concentrations of IL, making necessary the discovery of novel hydrolytic enzymes and fermentative microorganisms that are tolerant to ILs. In this review, the current state and the challenges of using ILs as a pretreatment of LC biomass was evaluated, underlining the advances in the discovery and identification of new IL-tolerant enzymes and microorganisms that could improve the bioprocessing of biomass to fuels and chemicals.     

Abundance and biomass of heterotrophic microorganisms in Lake Tanganyika

1. This study focused on heterotrophic microorganisms in the two main basins (north and south) of Lake Tanganyika during dry and wet seasons in 2002. Bacteria (81% cocci) were abundant (2.28–5.30 × 10⁶ cells mL^?1). During the dry season, in the south basin, bacterial biomass reached a maximum of 2.27 g C m^?2 and phytoplankton biomass was 3.75 g C m^?2 (integrated over a water column of 100 m). 2. Protozoan abundance was constituted of 99% of heterotrophic nanoflagellates (HNF). Communities of flagellates and bacteria consisted of very small but numerous cells. Flagellates were often the main planktonic compartment, with a biomass of 3.42–4.43 g C m^?2. Flagellate biomass was in the same range and often higher than the total autotrophic biomass (1.60–4.72 g C m^?2). 3. Total autotrophic carbon was partly sustained by the endosymbiotic zoochlorellae Strombidium. These ciliates were present only in the euphotic zone and usually contributed most of the biomass of ciliates. 4. Total heterotrophic ciliate biomass ranged between 0.35 and 0.44 g C m^?2. In 2002, heterotrophic microorganisms consisting of bacteria, flagellates and ciliates represented a large fraction of plankton. These results support the hypothesis that the microbial food web contributes to the high productivity of Lake Tanganyika. 5. As the sole source of carbon in the pelagic zone of this large lake is phytoplankton production, planktonic heterotrophs ultimately depend on autochthonous organic carbon, most probably dissolved organic carbon (DOC) from algal excretion.     

Full assessment of Sida (Sida hermaphrodita) biomass as a solid fuel

Due to an increased awareness of climate change and limited fossil resources, the demand for alternative energy carriers such as biomass has risen significantly during the past years. This development is supported by the idea of a transition to a bio‐based economy reducing fossil‐based carbon dioxide emissions. Based on this trend, biomass for energy is expected to be used in the EU mainly for heating until the end of the decade. The perennial herbaceous mallow plant Sida hermaphrodita (L.) Rusby (‘Sida’) has high potential as an alternative biomass plant for energy purposes. Different density cultivation scenarios of Sida accounting for 1, 2, or 4 plants per m² resulted in a total biomass yield of 21, 28, and 34 tons dry matter/ha, respectively, over a 3‐year period under agricultural conditions while the overall investment costs almost doubled from 2 to 4 plants per m². Subsequently, Sida biomass was used as SI) chips, SII) pellets, and SIII) briquettes for combustion studies at pilot plant scale. Pellets outcompeted chips and briquettes by showing low CO emission of 40 mg/Nm³, good burnout, and low slagging behavior, however, with elevated NO_x and SO₂ levels. In contrast, combustion of chips and briquettes displayed high CO emissions of >1,300 mg/Nm³, while SO₂ values were below 100 mg/Nm³. Contents of HCl in the flue gas ranged between 32 and 52 mg/Nm³ for all Sida fuels tested. High contents of alkaline earth metals such as CaO resulted in high ash melting points of up to 1,450°C. Life cycle assessment results showed the lowest ecological impact for Sida pellets taking all production parameters and environmental categories into consideration, showing further advantages of Sida over other alternative biomasses. Overall, the results indicate the improved applicability of pelletized Sida biomass as a renewable biogenic energy carrier for combustion.     

Regulation of the biomass and activity of soil microorganisms by microfauna

Microcosm experiments showed that the microbial biomass and the respiration activity in soil were regulated by nematodes. Depending on nematode number and plant residue composition, the trophic activity of nematodes can either stimulate or inhibit microbial growth and respiration as compared to soil containing no nematodes. The stimulating effect was observed when nitrogen-free (starch) or low-nitrogen (wheat straw, C : N = 87) organic substrates were applied. Inhibition occurred when a substrate rich in nitrogen (alfalfa meal, C : N = 28) was decomposed and the nematode population exceeded the naturally occurring level. A conceptual model was developed to describe trophic regulation by microfauna (nematodes) of the microbial productivity and respiration ctivity and decomposition of not readily decomposable organic matter in soil. The stimulating and inhibiting influence of microfauna on soil microorganisms was not a linear function of the rate of microbial consumption by nematodes. These effects are largely associated with the induced change in the physiological state of microorganisms rather than with the mobilization of biogenic elements from the decomposed microbial biomass.     

Regulation of the biomass and activity of soil microorganisms by microfauna

Microcosm experiments showed that the microbial biomass and the respiration activity in soil were regulated by nematodes. Depending on nematode number and plant residue composition, the trophic activity of nematodes can either stimulate or inhibit microbial growth and respiration as compared to soil containing no nematodes. The stimulating effect was observed when nitrogen-free (starch) or low-nitrogen (wheat straw, C:N = 87) organic substrates were applied. Inhibition occurred when a substrate rich in nitrogen (alfalfa meal, C:N = 28) was decomposed and the nematode population exceeded the naturally occurring level. A conceptual model was developed to describe trophic regulation by microfauna (nematodes) of the microbial productivity and respiration activity and decomposition of not readily decomposable organic matter in soil. The stimulating and inhibiting influence of microfauna on soil microorganisms was not a linear function of the rate of microbial consumption by nematodes. These effects are largely associated with the induced change in the physiological state of microorganisms rather than with the mobilization of biogenic elements from the decomposed microbial biomass.     

The problems associated with high biomass levels in plant cell suspensions

The development of plant cell cultures as an alternative supply of phytochemicals has been difficult. Although there has been some very suitable targets, the yields of these compounds has remained low despite considerable efforts. One of the main constituents of a process is its productivity which is the sum of the process run time (growth rate), yield, and biomass levels. The effect of changes in all three of these components on productivity has been demonstrated.Of the three components making up productivity, biomass is perhaps the easiest to increase. However, high biomass levels will increase the viscosity, which will affect both mixing and oxygen supply. Therefore, this will require more vigorous mixing which may increase the shear within the bioreactor. All these parameters need further investigation at high biomass concentrations.     

Macrophyte biomass in the Kiev reservoir (Ukraine)

This paper presents the results from research of a few macrophyte communities and their dominant stands in the Kiev Reservoir (Ukraine). Largely concentrated on the methodological aspects of biomass sampling in macrophyte communities.     

Biosynthesis of nicotinamide dinucleotide (NAD) in microorganisms (review of the literature)

Data on the biosynthesis of nicotinamide adenine dinucleotide (NAD) and mechanisms of its regulation in microorganisms are reviewed, and the reasons and conditions of NAD overproduction are discussed.     

Antibacterial activity of ZnO nanoparticle suspensions on a broad spectrum of microorganisms

Nanoparticle metal oxides represent a new class of important materials that are increasingly being developed for use in research and health-related applications. Highly ionic metal oxides are interesting not only for their wide variety of physical and chemical properties but also for their antibacterial activity. Although the in vitro antibacterial activity and efficacy of regular zinc oxides have been investigated, little is known about the antibacterial activity of nanoparticles of ZnO. Preliminary growth analysis data suggest that nanoparticles of ZnO have significantly higher antibacterial effects on Staphylococcus aureus than do five other metal oxide nanoparticles. In addition, studies have clearly demonstrated that ZnO nanoparticles have a wide range of antibacterial effects on a number of other microorganisms. The antibacterial activity of ZnO may be dependent on the size and the presence of normal visible light. The data suggest that ZnO nanoparticles have a potential application as a bacteriostatic agent in visible light and may have future applications in the development of derivative agents to control the spread and infection of a variety of bacterial strains.