Control of Microbial Adhesion as a Strategy for Food and Bioprocess Technology

Bacteria and other microorganisms have a natural tendency to adhere to surfaces as a survival mechanism. This can occur in many environments, including the living host, industrial systems, and natural waters. The general outcome of bacterial colonization of a surface is biofilm formation, which consists of microorganisms immobilized in a variety of polymeric compounds generally referred to as extracellular polymeric substances. Bacterial adhesion to a solid surface is a crucial step in the biofilm process. This step is dependent upon van der Waals, electrostatic, and acid–base interactions. These interactions are influenced by physicochemical properties of the substratum and the bacterial surface, such as hydrophobicity, surface charge, and electron donor–electron acceptor properties. In addition, the roughness of the substratum and the microbiological characteristics of the cell surface, such as cellular appendages and production of exopolysaccharides, can affect the adherence process. To date, many strategies have been developed to decrease the adherence of bacteria to surfaces. Surface modification with the addition of the suitable compounds makes surfaces less attractive for microorganisms and therefore prevents bacterial adherence and biofilm formation.     

Short rotation woody crop plantations in Brazil and the United States

The Short Rotation Woody Crop (SRWC) concept has been applied in the establishment of experimental and commercial plantations in both the United States and Brazil. The SRWC concept involves the application of agricultural principles to the production of tree crops for fiber or fuel. Although extensive SRWC research has occurred in the United States during the past 10 to 16 years, commercial applications have been rather limited. On the other hand, Brazil has made considerable progress in producing SRWC on a large-scale commercial basis while simultaneously conducting research. It seems clear that both countries can gain from each other's experience in SRWC experimentation and commercialization. This paper discusses and compares SRWC system developments in both countries and suggests means of improving and expanding SRWC systems use.     

Ripening of banana fruit monitored by water relaxation and diffusion 1H-NMR measurements

Water transverse relaxation times T₂ and self-diffusion coefficients D have been measured on banana samples at different ripening stages. Relaxation data have been interpreted on the basis of a chemical and diffusive exchange model proposed by Belton and Hills [Mol. Phys. 61(4) (1987) 999] and Hills et al. [Mol. Phys. 67(4) (1989) 903]. According to that model the observed increase of T₂ values of both cytoplasmatic and vacuolar water may be mainly attributed to the decrease of starch concentration during the ripening process. On the other hand, the observed water self-diffusion coefficient decrease is related to sugar accumulation as starch hydrolysis proceeds. At the early stages of ripening, the individual self-diffusion coefficient values of cytoplasmatic and vacuolar water differ from one another and have been calculated through the analysis of relaxation time-separated pulsed field gradient nuclear magnetic resonance experiments [J. Magn. Reson. A 112 (1995a) 237].     

Contact toxicity of filter cake and Triplex powders from Ethiopia against Sitophilus oryzae

Contact toxicity of filter cake and Triplex powders from Ethiopia were evaluated against the rice weevil, Sitophilus oryzae (Linnaeus). The study was aimed at determining the lethal and effective concentrations and times for both powders against S. oryzae. The lethal concentrations for 50 and 99% mortality (LC₅₀ and LC₉₉) of filter cake and Triplex against S. oryzae were determined at 14 d after exposing 10 adults for 12 h to concrete arenas inside Petri dishes treated with filter cake concentrations of 0.5–8 g/m² and Triplex concentrations of 1–9 g/m². Lethal times for 50 and 99% mortality (LT₅₀ and LT₉₉) were determined at 14 d after exposing adults for 1–24 h to 3 g/m² of filter cake and 9 g/m² of Triplex. Effective concentrations (EC₅₀ and EC₉₉) and times (ET₅₀ and ET₉₉) for 50 and 99% reduction of adult progeny production were determined from reduction in adult progeny production relative to production in control treatments at 42 d after exposure to filter cake and Triplex. LC₅₀ and LC₉₉ values for S. oryzae adults were 0.70 and 8.49 g/m², respectively, when exposed to filter cake and 2.27 and 21.38 g/m², respectively, when exposed to Triplex. The corresponding LT₅₀ and LT₉₉ values were 3.13 and 27.21 h, respectively, for filter cake and 4.72 and 38.60 h, respectively, for Triplex. EC₅₀ and EC₉₉ values for progeny reduction were 0.57 and 7.95 g/m², respectively, for filter cake and 2.77 and 18.82 g/m², respectively, for Triplex. The corresponding ET₅₀ and ET₉₉ values were 2.57 and 17.73 h, respectively for filter cake and 3.39 and 24.74 h, respectively, for Triplex. S. oryzae exposed to filter cake produced significantly less number of insect damaged kernels and grain weight loss than those exposed to Triplex. Filter cake was more efficacious against S. oryzae than Triplex.     

Significant population structure in Australian Cryptolestes ferrugineus and interpreting the potential spread of phosphine resistance

An analysis of the population genetics of Cryptolestes ferrugineus, across all major regions in Australia where grain is grown and stored in bulk, provides an initial step in investigating the movement of these insects and implications for the spread of phosphine resistance. Microsatellite data revealed two levels of genetic structure. Across Australia, two clusters were detected, one in eastern Australia (Queensland, New South Wales, Victoria and Tasmania) and Western Australia (Cluster 1) and one in South Australia (Cluster 2). Intermediate between them, in eastern South Australia, are a couple of populations that are equally admixed for the two clusters. Populations in Western Australia and western SA belong to different clusters suggesting that the extensive and arid Nullarbor Plain restricts the natural dispersal of these beetles. Isolation-by-distance and the detection of clustering among local populations suggests there is considerable gene flow at a local scale in C. ferrugineus, and we infer this is by flight. Limited natural gene flow between eastern and western Australia might, in part, explain why extremely high resistance has not been detected in Western Australia.     

Effect of light,food additives and heat on the stability of sorghum 3-deoxyanthocyanins in model beverages

This work aimed to evaluate the stability of sorghum 3-deoxyanthocyanins (DXA) in model beverages (pH 3.5) elaborated with crude sorghum phenolic extract, containing ascorbic acid and sulphite, under fluorescent light exposure and subjected to heat treatment. There was no significant difference in the DXA degradation during storage under light exposure (24.16%) and absence of light (20.72%). DXA degradation did not differ in the presence of ascorbic acid during storage under light exposure (23.99–25.38%) and absence of light (19.87–21.74%). The addition of sulphite caused an initial bleaching reaction, but as a reversible reaction, the anthocyanin content was higher on the last day of storage compared to the first day. There were no significant differences in total anthocyanin content of all treatments subjected to the heat treatment (80 °C for 5 and 25 min). Thus, crude DXA are very stable under light, additives and heat, and may be useful as natural food colourants.     

Comparison of three different wood ashes and diatomaceous earth in controlling the maize weevil under laboratory conditions

We studied the insecticidal effects of ashes from three different tree species (common beech, Norway spruce, and black locust) on the mortality of Sitophilus zeamais adults under laboratory conditions. A diatomaceous earth formulation, SilicoSec^® was used as a positive control. We studied the contact effects of ashes on adults and the insecticidal effect of ash mixed with wheat grain. The experiment was carried out at three different temperatures (15, 20 and 25 °C) and at two different relative humidity [r.h.] values (55% and 75%). The study on contact effects (immediate mortality and delayed mortality) was carried out in Petri dishes, where we applied ash in two concentrations, 10 and 20 g/m². After 7 d there was more than 97% mortality for the beetles in all three wood ashes at 25 °C and 55% R.h., while after 14 d wood ash of Norway spruce showed the highest effectiveness (87%) at 20 °C and 55% R.h. 96% mortality was recorded at 20 °C and 55%, when SilicoSec^® was applied. The experiment with the mixture of ashes and grains was performed by mixing 2.5 or 5 w% of ash with wheat. In both approaches, we established that lower R.h. in combination with higher temperatures led to higher adult mortality rates. Regardless of the approach, the preparation concentrations did not influence adult mortality. The most efficient ash was that of Norway spruce, yet we attribute its effectiveness not only to its highest content of SiO₂ (11.68%) but also to the other ingredients in ash, which can enhance its hygroscopic properties. Our research demonstrated that wood ash can efficiently protect stored crops from maize weevils. However, before introducing wood ash into the systems of protecting stored wheat grains against harmful insects, the influence of concentrations of ashes and their hygroscopic properties should be studied.     

An evaluation of the effectiveness of a chemical additive based on sodium benzoate,potassium sorbate,and sodium nitrite on the fermentation and aerobic stability of corn silage

We evaluated the effectiveness of an additive comprising sodium benzoate, potassium sorbate, and sodium nitrite (SSL) as active ingredients for its ability to improve the aerobic stability of corn silages made in North America. In experiment 1, treatment with SSL (1.5 and 2.0 L/t) on whole-plant corn (WPC) was compared with treatment with an additive containing buffered propionic acid and citric acid (BPA; 2 L/t) on corn harvested at 32 and 38% dry matter and ensiled for 120 d. Silage treated with BPA was higher in ammonia-N and propionic acid relative to other treatments. Treatments with all of the additives had numerically, but not statistically, fewer yeasts compared with untreated silage. Both application rates of SSL resulted in lower concentrations of ethanol compared with untreated and BPA silages. Treatment with BPA improved the aerobic stability of silages compared with untreated silage, but the effect from SSL was markedly greater. In experiment 2, WPC was untreated or treated with 2 or 3 L of SSL/t or a microbial inoculant containing Enterococcus faecium M74, Lactobacillus plantarum CH6072, and Lactobacillus buchneri LN1819 (final total lactic acid bacteria application rate of 150,000 cfu/g of fresh forage). Silages were air stressed for 24 h at 28 and 42 d of storage and ensiled for 49 d before opening. Inoculation had no effect on acid end products, ethanol, number of yeasts, or aerobic stability compared with other treatments. Treatment with SSL decreased the amount of ethanol, had no effect on number of yeasts, and improved aerobic stability in a dose-dependent manner compared with other treatments. In experiment 3, WPC was untreated or treated with 2 L of SSL/t and ensiled for 5, 15, and 30 d. Treatment with SSL resulted in silage with fewer yeasts and lower concentrations of ethanol after all times of ensiling compared with untreated silage. In addition, SSL improved aerobic stability after each period of ensiling, but the effect was more at 15 and 30 d compared with 5 d of storage. Treating WPC with SSL can improve the aerobic stability of corn silage made in North America, and the effect can be observed as soon as 5 d after ensiling.     

Lactational performance of dairy cows in response to supplementing N-acetyl-l-methionine as source of rumen-protected methionine

The objective of this experiment was to evaluate the effects of supplementing a rumen-protected source of Met, N-acetyl-l-methionine (NALM), on lactational performance and nitrogen metabolism in early- to mid-lactation dairy cows. Sixty multiparous Holstein dairy cows in early lactation (27 ± 4.3 d in milk, SD) were assigned to 4 treatments in a randomized complete block design. Cows were blocked by actual milk yield. Treatments were as follows: (1) no NALM (control); (2) 15 g/d of NALM (NALM15); (3) 30 g/d of NALM (NALM30); and (4) 45 g/d of NALM (NALM45). Diets were formulated using a Cornell Net Carbohydrate and Protein System (CNCPS) v.6.5 model software to meet or exceed nutritional requirements of lactating dairy cows producing 42 kg/d of milk and to undersupply metabolizable Met (control) or supply incremental amounts of NALM. The digestible Met (dMet) supply for control, NALM15, NALM30, and NALM45 were 54.7, 59.8, 64.7, and 72.2 g/d, respectively. The supply of dMet was 88, 94, 104, and 115% of dMet requirement for control, NALM15, NALM30, and NALM45, respectively. Milk yield data were collected, dry matter intake (DMI) was measured daily, and milk samples were collected twice per week for 22 wk. Blood, ruminal fluid, urine, and fecal samples were collected during the covariate period and during wk 4, 8, and 16. Data were analyzed using the GLIMMIX procedure of SAS (SAS Institute) using covariates in the model for all variables except body weight. Linear, quadratic, and cubic contrasts were also tested. Treatments did not affect DMI, milk yield, and milk component concentration and yield; however, feed efficiency expressed as milk yield per DMI and 3.5% fat-corrected milk per DMI were quadratically affected, with greater response observed for NALM15 and NALM30 compared with control. Acetate proportion linearly increased, whereas propionate proportion linearly decreased with NALM supplementation. Blood urea nitrogen linearly decreased with NALM supplementation. Total plasma essential AA concentrations were quadratically affected, as greater values were observed for control and NALM45 than other treatments. Plasma Met concentration was quadratically affected as lower levels were observed with NALM15, whereas Met concentrations increased with NALM45 compared with control. Nitrogen utilization efficiency and apparent total-tract nutrient digestibility were not affected by treatment. Supplementation of NALM at 15 or 30 g/head per day resulted in the greatest improvements in feed efficiency without affecting N metabolism of early- to mid-lactation dairy cows.