(2if) Enhancing the Bioconversion of Major Lignocellulosic Fractions to Medium Chain Length-Polyhydroxyalkanoates

My research focuses on the implementation and understanding of novel environmental engineering processes that could potentially provide sustainable solutions for lignocellulose biorefinery, CO₂ sequestration and bioconversion, and removal of emergent contaminants from wastewater. I have particular interest on the use of artificial consortia for efficient bioconversion and production of metabolites. My previous work on these areas received funds from Mexican (CONACYT) and UK (Newton Fund-British Council) agencies as PI or co-PI, having a positive impact on my academic productivity. Over the last 5 years, I have published an average of 4 papers per year (27 total) —most of them as first/corresponding author— in journals such as Green Chemistry (I. F. 10.2), Applied Energy (I. F. 9.7), Bioresource Technology (I.F. 9.6), ACS Sustainable Chemistry & Engineering (I.F. 8.2), etc. Moreover, during the last 2.5 years, I have worked at Texas A&M University together with a multidisciplinary team from different US Universities in projects funded by US agencies such as DOE and SBIR programs.

I have already developed concept papers with innovative ideas to seek funds for the next stage of my career. If presented with an opportunity my lab will investigate mechanisms and optimize the following bioprocesses.

1) Integral biorefinery for efficient bioconversion: This research area will integrate the most recent breakthroughs in holocellulose and lignin biotransformation into fungible bioproducts, including novel pretreatment, saccharification and build of synthetic cultures. The processes will be designed based on the chemical characteristics of the lignocellulosic materials, such as agave and corn stover.

2) CO₂ abatement via its bioconversion into fungible products: I will develop novel artificial consortia capable to produce acetate and other metabolites from CO2, based on the Wood–Ljungdahl pathway. These metabolites will serve as building blocks for further bioconversion to multiple products such as controlled-monomer unit PHAs.

3) Microplastic removal from wastewater and upcycling: Novel artificial consortia with different microorganisms including bacteria, fungi and microalgae will be developed to capture microplastics and upcycling to bioplastics.

Teaching Interests

Research and teaching are highly integrated and synergistic; one leads to the latest innovations while the other allows for the dissemination and discussion of such innovations. Moreover, teaching can also be a powerful tool to boost research by providing new ideas and hypotheses when active learning strategies such as research workshops, group problem-solving, and project-based learning are used in classroom. Students benefit from these strategies by expanding their knowledge and often their scores. In fact, several publications have reported the learning/score improvement of students when active learning is used in STEM courses. Therefore, I have committed my teaching philosophy to help students fulfilling their potential through the use of active learning methods, discussion of recent research breakthroughs and illustrating the applicability of the subjects. In the past I completed a six-month certification focused on Content and Language Integrated Learning (CLIL methodology) with active learning methods by EduCluster, Finland. Since then, I have taught several courses for undergraduate and graduate programs under the active learning philosophy.

Broadly speaking, I have interest in teaching environmental biotechnology courses under the active learning philosophy. My experience includes teaching for undergraduate and graduate programs. I have taught or participated in the instruction of the following courses for Universities in Mexico and the US: Biochemistry, Bioengineering, Biomass Pretreatment and Biofuels, Environmental Engineering, Experimental Design, and Wastewater Treatment.

Abstract

Biological lignin conversion to medium chain length-polyhydroxyalkanoates (mcl-PHA) has recently emerged as an attractive alternative to petroleum-based plastics due to the renewable nature of lignin and the value-added applications of mcl-PHA. Previous reports suggested that addition of limited glucose can improve mcl-PHA accumulation in Pseudomonas putida KT2440 grown in lignin substrates. Herein, we propose a biorefinery process to systematically release lignin and sugars from lignocellulosic biomass and evaluate the potential of co-utilization of all biomass components for conversion to mcl-PHA. Our results indicate that a sequential treatment composed of acid pretreatment, enzymatic hydrolysis and alkaline treatment produces a suitable lignin stream for mcl-PHA production in engineered P. putida. In addition, the PHA titer could be increased by 71% when the lignin stream (AH) was combined with the enzymatic hydrolysate (EH) at a ratio of 75:25. Higher ratios of EH:AH negatively affect mcl-PHA accumulation as well as mixtures with sugars from the acid hydrolysate. The optimization of the fermentation conditions, including the inoculum (OD₆₀₀) and substrate (soluble solid content (SSC)), was carried out by a central composite design. The optimal conditions were achieved at OD₆₀₀ = 2.17 and SSC = 68.28 g L^−1. Under these conditions, the titer increased 4.3 fold, achieving a mcl-PHA production of 1.38 g L^−1. Lignin characterization before and after fermentation by nuclear magnetic resonance and gas chromatography-mass spectrometry showed that p-coumarates were mainly consumed during the fermentation for mcl-PHA production. Overall, this biorefinery strategy allowed us to increase mcl-PHA production by utilizing the different lignocellulosic fractions. Unlike previous studies, no model substrates were utilized at any stage of the fermentation process, representing a step forward towards process feasibility.