Plant endophytic bacteria have received special attention in recent decades for their ability to improve plant response to multiple stresses. A positive effect of endophytes on plant’s ability to cope with drought, salinity, nitrogen deficiency, and pathogens have already been demonstrated in numerous studies, and recently this evidence was consolidated in a meta-analysis of published data. Endophytic bacteria have also been implicated in increasing resistance to heavy metals in plants; despite the important biotechnological applications of such effect in heavy metal bioremediation and agriculture, efforts to systematically analyze studies in this field have been limited. In this study, we address this task with the objective of establishing whether the findings made for other types of stresses extend to the response to heavy metals. Specifically, we seek to establish if plant inoculation with plant-growth promoting endophytic bacteria have an impact on their tolerance to heavy metal stress? We carried out a meta-analysis of the effect size of inoculation with endophytic bacteria on the host plant biomass in response to heavy metal stress (aluminum, arsenic, cadmium, copper, chromium, manganese, nickel, lead, and zinc), which included 27 (from 76 published in the last 10 years) studies under controlled conditions that evaluated 19 host plants and 20 bacterial genera. Our results suggest that endophytic bacteria increase the biomass production of host plants subjected to different heavy metals, indicating their effectiveness in protecting plants from a wide range of metal toxicities. Stress mitigation by the bacteria was similar among the different plant groups with the exception of non-accumulating plants that benefit most from the symbiotic association. Host identity and heavy metal concentration seem to influence the effect of the bacteria. Our analysis revealed that bacterial consortia provide the greatest benefit although the most common biotechnological applications are not directed towards them, and support the value of endophytic bacteria as an alternative to mitigate heavy metal stress in a wide variety of hosts.

Controlled fermentation processes have high potential for improving coffee quality. The effect of fermentation temperature on beverage quality was investigated with coffee cultivated at elevations between 1166 and 1928 m. A completely randomized design was carried out at five elevation ranges at 200 m intervals in five farms per elevation range, and two temperatures (15 °C and 30 °C), which were maintained in a temperature-controlled bioreactor. Each temperature-controlled fermentation batch had a spontaneous fermentation batch (control treatment). Microbial identification of LAB and yeast was performed using a Biolog™ MicroStation™ ID System, and cup quality tests were performed following the SCA protocol. Tests conducted at 15 °C showed higher microbial community activity on the substrates used, indicating greater transformation potential than those conducted at 30 °C or those of spontaneous fermentation. According to Wilcoxon and Kruskal–Wallis tests, temperature-controlled fermentation resulted in high-quality coffee for all elevation ranges, with coffee from higher elevations and processed at controlled temperatures of 15 °C receiving the highest cup scores compared to coffee that was subjected to 30 °C. These results suggest that controlled temperature can be used to design standardized fermentation processes in order to enhance coffee quality through differentiated sensory profiles.

Biochar is a solid material obtained from the thermal decomposition of biomass of diverse biological origins through a process called pyrolysis. Biochar has great potential for reducing greenhouse gas emissions, sequester carbon in the soil, rehabilitate degraded soils, and reduce dependence on chemical fertilizers in crops. It also improves the physical, chemical, and biological properties of the soil and has a positive effect on plant growth. Given these attributes, there is a growing interest for adopting its use in agriculture, soil and land reclamation, and climate change mitigation. The effects of biochar application can be neutral or positive and will be determined mainly by factors such as the origin of the raw materials, carbonization conditions, frequency of applications, the method of application and dosage. In this review, we offer a detailed examination of the origins of biochar and the technologies used for its production. We examine the various materials that have been used to produce biochars and how they affect their physico-chemical characteristics, and we describe their applications in agriculture and climate change mitigation. Finally, we list the guides that describe the standards for the production, characterization, and commercialization of biochar that seek to guarantee the quality of the product and the essential characteristics for its safe use.